Students' use of anatomy modules in problem-based medical education at McMaster University.

BACKGROUND: The McMaster University Faculty of Health Sciences has a collection of self-directed anatomy learning modules that are available to help medical students prepare for tutorial discussions of health care problems. How students use this resource has never been adequately surveyed. METHOD: The rates of, patterns of, and reasons for module use among the 200 students in their first and second years were surveyed by questionnaire in late 1992. Responses were analyzed with contingency tables. RESULTS: Questionnaires were completed by 80 students (52 in their first year and 28 in their second). Anatomy module use depended not only on the students' levels in the program (i.e., curriculum years), but also on their pre-medical backgrounds in biology. The students did not use modules because their tutors and clinical-skills preceptors required it. The students who worked through modules considered themselves better prepared for tutorials, where their learning was evaluated. CONCLUSION: Though use of this resource varied among individuals, most McMaster students believed that module use helped them to make useful contributions to tutorial discussions.

Heinz-body hemolytic anemia from the ingestion of crude oil: a primary toxic effect in marine birds.

Hemolytic anemia developed in young herring gulls and Atlantic puffins given daily oral doses of a Prudhoe Bay crude oil. Anemia developed 4 to 5 days after the initiation of oil ingestion and was accompanied by Heinz-body formation and a strong regenerative response. The data evince a toxic effect on circulating red blood cells involving an oxidative biochemical mechanism and the first clear evidence of a primary mechanism of toxicity from the ingestion of crude oil by birds.

Separable assembly of platelet pseudopodal and contractile cytoskeletons.

Unactivated platelets contain about 69% G actin and less than 10% of the contractile proteins in a cytoskeletal core resistant to extraction with 1% Triton X-100. Activation by thrombin leads, within 1 min, to the formation of pseudopodia and contractile gels, accompanied by the reduction of the G-actin content to about 22% and the development of cytoskeletal cores containing 70%-80% of the total actin and 60%-80% of the total myosin and actin-binding protein. Inhibition of pseudopodal formation by pretreatment with cytochalasin B before thrombin activation results in the loss of most of the actin-binding protein and about one third of the actin from the cytoskeletal core. Myosin incorporation and contractile gel formation are unaltered by this treatment. Conversely, activation with phorbol 12-myristate 13-acetate leads to pseudopodal but not contractile gel formation, with cytoskeletal cores containing mostly actin and actin-binding protein. These results demonstrate that there are separable cytoskeletal assembly processes in platelets for pseudopodal and contractile gel formation.

Regeneration of afferent and efferent fibres to muscle spindles after nerve injury in adults cats.

1. The nerves to cat peroneus longus and tenuissimus muscles were either cut or crushed close to the muscle and the afferent and efferent nerve supply to the muscle spindles was studied electrophysiologically between 2 and 32 weeks later. 2. Recovery was more rapid and complete after crush than section for both afferent and efferent fibres. After recovery from either procedure normal primary and secondary afferents and static and dynamic gamma efferent fibres were found. 3. Some abnormally occurring neurones were found. One group consisted of beta fibres which had a static action on muscle spindles. Static beta fibres are very rarely found in normal muscles. 4. The results indicate that some guidance mechanism exists which after crush injuries of nerves may restore muscle receptor function almost to normal. Even after nerve section some muscle spindles may become correctly reinnervated.

Pyruvate inhibition of the carbon dioxide fixation of the strict chemolithotroph Thiobacillus thiooxidans.

A flow-through dialysis system used to decrease the concentrations of toxic organic materials excreted by Thiobacillus thiooxidans permitted an improved efficiency of carbon dioxide fixation when compared with cells taken from the usual shaken culture. The additions of various concentrations of pyruvic acid and succinic acid inhibited growth significantly. Pyruvate at a concentration of 5 X 10(-3) M completely inhibited the respiration of resting cells oxidizing sulfur. The toxicity of pyruvic acid was found to be permanent as evidenced by the inability to obtain satisfactory oxidation rates after washing the exposed cells twice in buffer. Both pyruvate (10(-3) M) and succinate (10(-3) M) inhibited carbon dioxide fixation by 84%.

Growth inhibition of Rhodopseudomonas capsulata by methylmercury acetate.

Growth of Rhodopseudomonas capsulata was inhibited in a bacteriostatic manner by as little as 10-minus 8 M methylmercury acetate (MeHgAc) in unsupplemented synthetic liquid medium or when cells were exposed to 8.0 nm of MeHgAc per mg of cell protein in a single exposure.

Multiple-variant design for the enrichment of photosynthetic bacterial populations.

A design for the simultaneous variation of acetate, sulfide, and sulfate concentrations in 11 related media is described. Selectivity of these media by a direct enumeration technique in solid culture was compared with that for enrichment in liquid culture. Variation of nutritional parameters resulted in the selection of Rhodospirillaceae at initial enrichment concentrations of 0.1 g or less of Na2S-9 H2O per litre and Chromatiaceae at 0.1 to 1.0 g of g of Na2S-9 H2O per litre. The survival of sulfate-reducing and coliform bacteria indicated interdependency of photosynthetic populations with the former and competition with the latter. Photosynthetic bacteria selectively cultivated in liquid enrichment were tentatively identified as Rhodopseudomonas capsulata, Rhodopseudomonas speroides. Chromatium warmingii, Chromatium okenii, Thiospirillum, and Rhabdomonas.

An investigation into the site of termination of static gamma fibres within muscle spindles of the cat peroneus longus muscle.

1. The distribution of static fusimotor fibres to intrafusal muscle fibres of cat peroneus longus muscle spindles was investigated using the glycogen-depletion technique of Edström & Kugelberg (1968). Single static gamma fibres were stimulation intermittently at high rates for 3 hr with the blood supply occluded for some of this time. Subsequently the portion of muscle containing the activated spindles was fixed, sectioned and stained for glycogen with the periodic acid-Schiff (PAS) method. 2. Ten static axons caused depletion in eleven spindles. In five of these the only glycogen-depleted fibres were nuclear chain fibres. In the other six spindles one nuclear bag fibre was depleted in addition to chain fibres and this was always the larger of the two within the spindle. 3. These results on a medium-sized hind limb muscle are compared with findings concerning the distribution of static gamma fibre axons previously investigated only in very small muscles. The results agree in showing that nearly all static gamma fibres innervate nuclear chain fibres but that in 50-75% of the times in which static gamma fibres innervate spindles the distribution is to bag fibres as well as to chain fibres. The interpretation to be put upon this is uncertain. One possibility with which the results from peroneus longus are consistent is that the bag fibres which are usually innervated by static axons are the 'intermediate' bag fibres whose ultrastructure has recently been shown to resemble that of chain fibres.

Studies on the site of termination of static and dynamic fusimotor fibres within muscle spindles of the tenuissimus muscle of the cat.

1. The site of termination of static and dynamic fusimotor fibres has been mapped by finding which intrafusal muscle fibres have been depleted of glycogen as a result of tetanic stimulation of single gamma fibres. Long periods of stimulation coupled with occlusion of the blood supply were necessary to cause glycogen depletion.2. In cat tenuissimus muscle, dynamic gamma motor fibres always activated bag intrafusal muscle fibres, and occasionally chain fibres. Static gamma fibres always activated chain fibres and frequently activated bag fibres as well.3. It is argued that these results can be fitted into the hypothesis of the mechanism of internal functioning of the spindle originally proposed by Jansen & Matthews (1962). It is also pointed out that the results raise problems concerning the mechanism of development of the spindle motor innervation.

Absorption and utilization of organic matter by the strict autotroph, Thiobacillus thiooxidans, with special reference to aspartic acid.

Butler, Richard G. (Rutgers, The State University, New Brunswick, N.J.), and Wayne W. Umbreit. Absorption and utilization of organic matter by the strict autotroph, Thiobacillus thiooxidans, with special reference to aspartic acid. J. Bacteriol. 91:661-666. 1966.-The strictly autotrophic bacterium, Thiobacillus thiooxidans, can be shown to assimilate a variety of organic materials. Aspartic acid can be assimilated into protein and can be converted into CO(2), but even in the presence of sulfur it cannot serve as the sole source of carbon for growth. The reason appears to be that aspartic acid is converted into inhibitory materials.