Cytological characterization of heterochromatin and rDNA inPinus radiata andP. taeda

Fluorochrome C-banding ofPinus radiata andP. taeda metaphase chromosomes showed many pericentromeric DAPI bands and interstitial CMA bands inP. radiata, and centromeric and interstitial CMA bands inP. taeda. Giemsa C-band patterns differed between the species with centromeric bands inP. radiata but no consistent bands inP. taeda. A karyotype ofP. radiata was developed based on banding patterns that distinguished all but two of the 12 pairs of chromosomes. In situ hybridization (ISH) using probes for high-copy ribosomal DNA (rDNA) showed 10 pairs of 18S–25S sites and two pairs of 5S sites in both species. Most of the sites were interstitial or centromeric.     

Biofilms and biodiversity: an interactive exploration of aquatic microbial biotechnology and ecology

The study of biofilms provides a unique educational opportunity to examine ecosystems, biodiversity and applications of environmental biotechnology. There are many variables that could be studied for measuring the interactions between bacterial biofilms and invertebrate biodiversity as a method for assessing the health of aquatic ecosystems. These interactions also lend themselves to an easily replicated model system which can be used to reach a wide audience with an educational opportunity for students as well as a professional development opportunity for teachers. At the foundation of the research are invaluable basic microbiology skills: strain collection, isolation, cultivation and characterization. Through the additional process of characterizing, identifying and enumerating invertebrate organisms that attach to bacterial biofilms in aquatic ecosystems, there evolved a multidisciplinary class laboratory activity that has found broad application. This activity is captivating not only to undergraduate microbiology students but to middle and high school students and their teachers. The demand for information about the activity has led to the development of a truly interactive web-based lesson, which in turn has resulted in additional inquiries and further refinement of the lesson as an undergraduate independent research course. Both of these are freely accessible on the web, with growing international participation and data exchange. Journal of Industrial Microbiology & Biotechnology (2000) 24, 334–338. Received 19 April 1999/ Accepted in revised form 17 February 2000     

Mechanisms of Hearing Loss after Blast Injury to the Ear

Given the frequent use of improvised explosive devices (IEDs) around the world, the study of traumatic blast injuries is of increasing interest. The ear is the most common organ affected by blast injury because it is the body’s most sensitive pressure transducer. We fabricated a blast chamber to re-create blast profiles similar to that of IEDs and used it to develop a reproducible mouse model to study blast-induced hearing loss. The tympanic membrane was perforated in all mice after blast exposure and found to heal spontaneously. Micro-computed tomography demonstrated no evidence for middle ear or otic capsule injuries; however, the healed tympanic membrane was thickened. Auditory brainstem response and distortion product otoacoustic emission threshold shifts were found to be correlated with blast intensity. As well, these threshold shifts were larger than those found in control mice that underwent surgical perforation of their tympanic membranes, indicating cochlear trauma. Histological studies one week and three months after the blast demonstrated no disruption or damage to the intra-cochlear membranes. However, there was loss of outer hair cells (OHCs) within the basal turn of the cochlea and decreased spiral ganglion neurons (SGNs) and afferent nerve synapses. Using our mouse model that recapitulates human IED exposure, our results identify that the mechanisms underlying blast-induced hearing loss does not include gross membranous rupture as is commonly believed. Instead, there is both OHC and SGN loss that produce auditory dysfunction.     

Cytogenetic analysis of lymphoblastoid cell lines

Cytogenetic abnormalities were discovered in more than half of 16 lymphoblastoid cell lines established from fragile X individuals and their relatives upon routine cytogenetic analysis of early passage cultures. Subsequently, a second series of lymphoblastoid lines was analyzed to determine if the aneuploidy was a characteristic of lymphoblastoid cell lines derived from fragile X families or a result of the use of cyclosporin A in the establishment of these lines. In the second series of 33 lymphoblastoid cultures, no aneuploid clones were found in the fragile X group, while two were detected in the control cultures, one in a line initiated with cyclosporin A and the other in a line established without cyclosporin A. We conclude that the abnormal clones in our preliminary series were not a characteristic of lines derived from fragile X families and probably not due to the use of cyclosporin A. However, the finding of chromosome abnormalities in a large proportion of lines during the first 3 mo of culture contrasts with previous reports of chromosome stability for the first 12-18 mo of cultivation and indicates that the chromosomes of lymphoblastoid lines should be monitored in any experiment in which a normal diploid complement is critical.     

The effect of hypoxia on performance during 30 s or 45 s of supramaximal exercise

The purpose of this study was to evaluate the effect of hypoxia (10.8 +/- 0.6% oxygen) on performance of 30 s and 45 s of supramaximal dynamic exercise. Twelve males were randomly allocated to perform either a 30 s or 45 s Wingate test (WT) on two occasions (hypoxia and room air) with a minimum of 1 week between tests. After a 5-min warm-up at 120 W subjects breathed the appropriate gas mixture from a wet spirometer during a 5-min rest period. Resting blood oxygen saturation was monitored with an ear oximeter and averaged 97.8 +/- 1.5% and 83.2 +/- 1.9% for the air (normoxic) and hypoxic conditions, respectively, immediately prior to the WT. Following all WT trials, subjects breathed room air for a 10-min passive recovery period. Muscle biopsies from the vastus lateralis were taken prior to and immediately following WT. Arterialized blood samples, for lactate and blood gases, were taken before and after both the warm-up and the performance of WT, and throughout the recovery period. Open-circuit spirometry was used to calculate the total oxygen consumption (VO2), carbon dioxide production and expired ventilation during WT. Hypoxia did not impair the performance of the 30-s or 45-s WT. VO2 was reduced during the 45-s hypoxic WT (1.71 +/- 0.21 l) compared with the normoxic trial (2.16 +/- 0.26 l), but there was no change during the 30-s test (1.22 +/- 0.11 vs 1.04 +/- 0.17 l for the normoxic and hypoxic conditions, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Induction of peritoneal ascites fluid by Freund's adjuvant: Genetic and hormonal influences.

Strain differences among inbred mice is demonstrated for the relative amounts of peritoneal ascites fluid induced by the injection of Freund's adjuvant and antigen. Females tend to produce more fluid than males; the lower level in males is attributable to the action of male hormone. Both genetic and epigenetic factors are determinants in the response levels; genetic factors differentiate the inbred strains of mice, epigenetic factors underlie the variations within a strain and the difference between sexes.     

On the propagation of a disturbance through a viscous liquid flowing in a distensible tube of appreciable mass

The velocity of propagation of a disturbance wave in a liquid flowing in a distensible tube is computed. The mathematical model is more general than those used in previous analyses: the tube wall properties are realistic; the convective part of the axial inertia forces is taken into account; radial inertia forces of both the fluid and tube wall are present; viscous stresses are present. Four parameters influencing the velocity of propagation are obtained and discussed. Curves are plotted illustrating the effects of the parameters. Contrary to the results of previous analyses, viscous effects are shown to be appreciable in blood flow. It is also shown that radial inertia effects can be important in laboratory set-ups. The material presented in this paper was adapted from the Ph.D. thesis written by the author at Harvard University.     

Structural chromosome abnormalities in Down syndrome: a study of two families.

Two families were ascertained through a proband with Down syndrome and a structural rearrangement involving two chromosomes 21. It is suggested that in one patient the chromosome is an isochromosome formed by misdivision of the centromere of a maternal telocentric chromosome 21 and that in the other a Robertsonian translocation involving chromosome 21 was inherited from the mother, who is a 46,XX/46,XX, -21,+t(21q21q) mosaic. The origin of the mosaicism is discussed and considered to be likely to be the result of breakage and reunion at the chromatid, rather than the chromosome, level.