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Biomedical subjects

M Mann

Publications and source records attributed to M Mann.

At least 235 records · Page 13Linked to original sources
PubMed1983

Effect of calcium and phosphorus on the gastrointestinal absorption of 203Pb in man.

Calcium and phosphorus were mainly responsible for reducing the gastrointestinal absorption of lead in human subjects. The effect of calcium was greater than phosphorus, and their combined effect was more than additive. Increasing weights of calcium and phosphorus progressively reduced lead absorption. The relationship between absorption and increasing weights could be described by two negative exponentials. These effects could be explained if lead competed with calcium and phosphorus for common transport mechanisms in the gut. Milk was also found to reduce lead absorption. Adding milk to the diet of people with low dietary calcium intake could reduce the possibility of increased absorption of ingested lead.

Animals↗
PubMed1983

Intermale aggression and infanticide in aged C57BL/6J male mice: behavioral deficits are not related to serum testosterone (T) levels and are not recovered by supplemental T.

Healthy aged adult (24-26 months of age) and young adult (2-4 months of age) c57BL/6J male mice were assessed for intermale aggression, pup-killing behavior (infanticide), and circulating levels of testosterone (T). When compared to young adult male mice, aged adult males were highly variable in the exhibition of both androgen-dependent behaviors. Significant numbers of aged males exhibited deficits in aggression and pup-killing while other animals were as behaviorally active as their young male counterparts. Assessment of serum T showed that aging did not produce a reduction in levels of the steroid and individual variability in androgen-dependent behavior of aged males was not related to plasma levels of the hormone. When aged non-aggressive and non-killer males were exposed to supplemental T by way of subcutaneously implanted silastic capsules, circulating levels of the steroid were elevated but T-dependent behavior was not recovered. These findings, in combination with those previously reported for copulatory behavior, indicate that the deficits observed in the androgen-dependent behavior of aged male mice cannot be attributed to a breakdown in the production of testicular androgens. While neural refractoriness to T may account in part for deficits in androgen-dependent behavior of aged males, the variability that is observed in the reproductive behaviors of aged male rodents ultimately may be related to other sources of variation such as the perinatal environment.

Aggression↗
PubMed1982

Characterization of spermatid/sperm basic chromosomal proteins in the genus Xenopus (Anura, Pipidae).

Spermatid/sperm basic chromosomal proteins from 17 species and subspecies of the genus Xenopus (Anura, Pipidae) were compared. Electrophoresis on acetic acid/urea/Triton X-100 polyacrylamide gels revealed that each Xenopus species with a diploid chromosome number of 36, 72, or 108 showed multiple, diverse spermatid/sperm-specific basic chromatin proteins with mobilities greater than the somatic histones. The numbers and mobilities of these proteins were characteristic of each Xenopus species and each subspecies of Xenopus laevis. Cytochemical tests revealed that the sperm basic nuclear proteins of these Xenopus species and subspecies were rich in arginine and lysine and contained more arginine than the nuclear proteins of somatic cells. X. tropicalis (2n = 20) and X. sp. n. (Zaire) displayed spermatid/sperm-specific basic chromatin proteins which migrated within the histone H1 region of acetic acid/urea/Triton X-100 polyacrylamide gels. Cytochemically the sperm nuclei of these species resembled those of somatic cells. These observations suggest that spermatid/sperm basic nuclear proteins can be used as molecular markers for individual species and subspecies of the genus Xenopus.

Animals↗
PubMed1982

Determinants of sperm nuclear shaping in the genus Xenopus.

The morphogenesis of sperm nuclei was investigated in six different species or subspecies of the genus Xenopus (Pipidae, Anura). The sequence of nuclear morphogenesis was similar in each species used in this study. Electrophoretic comparison of the basic chromatin proteins from late spermatids and sperm of each species demonstrated that the complements of histones and spermatid-sperm-specific basic proteins were extremely diverse suggesting that shape was not determined by specific basic proteins or mechanisms of histone removal. This conclusion was reinforced by the observation that Xenopus sperm DNA decondensed by 2.0 M NaCl remained contained in residual structures which resembled intact sperm nuclei. These observations suggested that morphogenesis of sperm nuclei is directed by proteins or RNA molecules which are not directly responsible for chromatin condensation.

Animals↗
PubMed1982

[Current status of thrombocyte and granulocyte substitution].

The present situation in thrombocyte and granulocyte substitution is presented. First, the different methods of producing thrombocyte and granulocyte concentrates are discussed. Differential centrifugation and cell separators with continuous or intermittent flow are used for gaining thrombocytes, whereas cell separators with continuous or intermittent flow as well as filtration and gravitation leucapheresis may be used for producing granulocyte concentrates. Then, the indications for substituting granulocytes and thrombocytes are discussed. For thrombocyte substitution, thrombocyte numbers below 20 X 10(9)/1 and haemorrhagic diathesis are considered as an absolute indication. Granulocyte concentrates should only be administered to patients with transitory marked granulocytopenia, with granulocytes being less than 0.2 X 10(9)/1 and ensured bacterial infection. Finally, future basic developments of thrombocyte and granulocyte substitution are discussed.

Blood Transfusion↗
PubMed1982

Developmental and differential aspects of mental rotation in early adolescence.

A chronometric mental rotation paradigm was applied to examine manipulation of visual imagery in early adolescence in relation to age, sex, mental rotation ability (measured psychometrically), and socioeconomic background. Fifth- and seventh-grade boys and girls from middle and lower socioeconomic backgrounds viewed tachistiscopically letters of the alphabet presented at 0 degrees, 60 degrees, 120 degrees, and 180 degrees of rotation and were asked to judge whether the letter was forward or backward. In one condition, children were given no information about the test letter, and in the other, advance visual information about its identity and orientation was provided. With age, children became more skillful at rotating and were more likely to show evidence of using the advance information as a visual image. There were no sex differences. Socioeconomic differences were more pronounced in the fifth than the seventh grade. Children showing high mental rotation ability were more likely than low-ability children to show evidence of rotating visual stimuli on the chronometric measure. The findings are discussed in terms of adolescent cognitive development.

Age Factors↗
PubMed1981

Discitis--a rare early symptom of ankylosing spondylitis.

This case report describes a patient who suffered from backache at the age of 12 years. The initial diagnosis was Scheuermann's disease but repeated examinations showed a progressive discitis, without signs of arthritis of the sacro-iliac joints. There was also a recurring effusion of the left knee. Three years later the clinical and radiological evaluation showed irreversible immobilisation of the dorsolumbar spine, whereas the sacro-iliac joints were mildly affected. Discitis seems to be a rare early symptom of ankylosing spondylitis.

Adolescent↗
PubMed1981

Continuous blood pressure measurement in rats with aortic baroreceptor deafferentation.

The purpose of this study was to determine if once-daily arterial pressure measurements are a reliable estimate of actual time-averaged arterial pressure in neurogenic hypertensive rats. Male rats were subjected to either aortic baroreceptor deafferentation (ABD, n = 10) or sham operation (SO, n = 10). One to 3 mo later, arterial pressure (AP) was recorded from a chronic indwelling catheter in each rat for 72 continuous hours. Subsequently, AP was determined once a day (10- to 30-min recording periods) in each rat for an additional 3 consecutive days. Continuous recording yielded an average mean arterial pressure (MAP) of 104 +/- 2 mmHg in SO rats and an average mean MAP of 120 +/- 3 mmHg in ABD rats. Standard deviation of MAP measured every 5 min for 24 consecutive hours (as an index of pressure lability) was 8.0 +/- 0.4 mmHg in SO rats and 14.4 +/- 1.3 mmHg in ABD rats. Both of the above differences were statistically significant (P less than 0.05). The average MAP from daily measurements in the same rats was 107 +/- 3 mmHg in SO rats and 124 +/- 3 mmHg in ABD rats. Average pressure values were not statistically different for the two measurement techniques in either group of rats. Overall, there existed a significant correlation (r = 0.64, P less than 0.01) between MAP measured continuously and daily in the 20 rats studied. We conclude that daily direct measurement of MAP in conscious ABD rats yields a satisfactory estimate of actual time-averaged MAP in these rats despite their markedly increased MAP lability.

Afferent Pathways↗