Arrangement of pili in colonies of Neisseria gonorrhoeae.

The morphology and arrangement of pili in the P++ colony phenotype of Neisseria gonorrhoeae were examined by a variety of electron microscopic techniques. The apparent structure and organization of gonococcal pili varied depending upon the method of specimen preparation. Pili as thin, individual, unbranched structures were demonstrated by negative staining and in sections of epoxy-embedded specimens. Pili forming thick structures which branch, subdivide, and rejoin to form an irregular lattice were demonstrated in specimens processed by the critical-point drying method and by rapid freezing and low temperature sublimination. We propose that in gonococcal colonies of the P++ phenotype, pili exist as individual threadlike structures only on the bacterial surfaces; as the pili leave the bacterial surfaces, they form thick bundles which branch, subdivide, and rejoin to form a supporting framework interconnecting the colony members. This arrangement of pili is usually disrupted by the commonly used method of negative staining and cannot be clearly detected within epoxy-embedded specimens. These data are summarized in a model depicting the organization of pili in the P++ colony phenotype of N. gonorrhoeae.     

Comparative foraging behavior of Neotropical robber flies (Diptera: Asilidae)

Summary Robber fly species within a Panamanian rain forest comprised distinct shade-seeking (SS) and light-seeking (LS) groups. Thoracic temperatures of LS species averaged 9.2°C greater than ambient, whereas those of SS species averaged only 1.3°C above ambient. Among SS species, attack rate decreased with increasing body mass, whereas relocation rate and attack and relocation distances increased with increasing body mass. Attack and relocation distances of LS species were similar to those of SS species of similar size. Large (>100 mg) LS species, however, had much higher attack and relocation rates than large SS species. The potential costs and benefits of basking are briefly discussed.     

Perception of solid shape from shading

Observers judged the slants and tilts of numerous regions within shaded images of ellipsoid surfaces that varied in shape, orientation, surface reflectance, and direction of illumination. The perceived three-dimensional structure of each surface was calculated from these judgments. Much of the error in observers' responses resulted from a tendency to perceive surfaces whose axes were aligned with the display screen. The presence of specular highlights or cast shadows, in contrast, had no effect on performance. The results of the experiment indicate that several assumption of certain formal models for perception of shape from shading are not psychologically valid. The most notable of these assumptions are that the visual system initially assumes that all surfaces have Lambertian reflectance and that illuminant direction must be known before shape detection can proceed. These assumptions are often accompanied by a third assumption that surface orientation is detected locally, and global shape determined by smoothing over local surface orientation estimates. The present experiment indicates that an alternative approach offered by Koenderink and van Doorn may be more psychologically accurate, as it avoids all three assumptions.Supported in part by the Air Force Office of Scientific Research (AFOSR 82-0148). The research reported in this paper was performed while the first author was a graduate student at the University of Connecticut at Storrs     

Expression of terminal deoxynucleotidyl transferase in human thymus during ontogeny and development

Expression of the enzyme terminal deoxynucleotidyl transferase (TdT) was studied in human thymus during ontogeny and development. In five fetal thymus samples, the enzyme activity was barely detectable. At birth, the terminal transferase activity remained low. Maximum expression of the enzyme activity occurred between 10 and 40 mo of age. Analysis of six other enzyme activities, adenosine kinase, deoxyadenosine kinase, AMP deaminase, dAMP deaminase, 5' nucleotidase, and adenosine deaminase confirmed the normal status of the thymic tissue. A careful analysis of thymic architecture revealed that involution did not occur as a result of the disease process that necessitated cardiac surgery. By immunofluorescence, the TdT antigen was localized exclusively in the nucleus of cortical thymocytes. Protein immunoblotting studies indicated that human thymic terminal transferase exists as a single high m.w. species in individuals under 30 mo of age. Thereafter, a variant m.w. species is detectable. The increase in expression of this enzyme coincides with the increase observed in serum immunoglobulin levels during maturation and precedes the maximum development of the human thymus.     

Identification of penicillin-binding protein 5a of Bacillus megaterium KM as a DD-carboxypeptidase.

Measurement of the stabilities of DD-carboxypeptidase activity and the penicillin-binding activity of proteins 5 and 5a in membranes isolated from vegetative cells and stage-V forespores suggests that the unique sporulation-specific protein 5a may be a penicillin-sensitive DD-carboxypeptidase.     

Total Hip Replacement in Osteoarthrosis using the Charnley Prosthesis

Charnley low-friction arthroplasty was performed on 352 osteoarthritic hips, usually because of severe pain. Three hundred and twenty hips were reviewed at a special follow-up clinic or by postal questionnaire. After operation 89% of hips were pain-free or caused only occasional discomfort, and in 76% there was an increased range of movement. Of those patients actually seen for review 79% were judged to have a good or excellent result. The most frequent single complication was deep infection, which occurred in 5·3% of hips.     

Glucose Tolerance and Serum Insulin in Identical Twins of Diabetics

Glucose tolerance with serum insulin assay has been carried out in 24 apparently unaffected identical twins of diabetics. Glucose values were significantly higher and insulin values significantly lower than in control subjects, but there was considerable individual variation and in half the cases glucose tolerance was normal. There was no case of increased insulin response. In these twins glucose tolerance and insulin response were not correlated with weight, family history of diabetes, age at diagnosis of diabetes in the affected twin, time since that diagnosis, nor with age at testing the unaffected twin. On retesting 12 of the twins after two years no significant differences were found from the first testing.We conclude that not all these twins are likely to develop diabetes, that the assumption that identical twins of diabetics are necessarily “prediabetic” is probably erroneous, and that factors other than genetic ones are important in the aetiology of diabetes.     

Mallory Weiss Syndrome

Head injury in infants and young children may produce lesions that are relatively unique for this age group. The uniqueness is generally due to the structural immaturity of the skull, meninges and brain.“Derby-hat” and diastatic fractures are common in this age group. Spurious meningoceles result from tearing of the dura which is closely adherent to the skull. The syndrome of “delayed” concussion is more commonly manifested in children. Extradural and subdural hemorrhage may develop from lacerations of the major venous sinuses. A classical extradural hematoma may occur in the absence of fracture across meningeal arterial channels.The management of patients with head injury has been improved by the more frequent use of tracheotomy, hypothermic techniques and drugs of the “lytic cocktail.” Solutions of urea in 10 per cent invert sugar are administered intravenously to control cerebral edema in selected patients.