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We examined karyotypes of the endemic New Zealand reptile genus Sphenodon (tuatara) from five populations, finding a karyotype unchanged for at least one million years. Animals karyotyped were from five geographically distinct populations, representing three groups, namely S. guntheri, S. punctatus (Cook Strait group), and S. punctatus (northeastern North Island group). All five populations have a diploid chromosome number of 2n = 36, consisting of 14 pairs of macrochromosomes and four pairs of microchromosomes. Chromosomal differences were not found between the five populations nor between female and male animals, except for one animal with a structural heteromorphism. Similarity between Sphenodon and Testudine karyotypes suggests an ancestral karyotype with a macrochromosome complement of 14 pairs and the ability to accumulate variable numbers of microchromosome pairs. Our research supports molecular phylogenies of the Reptilia. Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

We examined the three-dimensional arrangement of bivalents and, in particular, a chain of four chromosomes (chain quadrivalent) in the metaphase I spindle of pollen mother cells of Allium triquetrum by confocal microscopy. Firstly, we show by optical sectioning and three-dimensional image reconstruction that the cooriented pairs of centromeres of all seven bivalents lie virtually parallel to each other in the metaphase I spindle, parallel to the long axis of the spindle. Secondly, we like-wise show that the four centromeres of the chain quadrivalent are aligned in the metaphase I spindle in, essentially, a two-dimensional array, not in a three-dimensional array, as proposed by some other authors. This two-dimensionality has its basis, we argue, in the principle that poleward directed spindle forces minimise centromere-to-pole distances and therefore align pairs of centromeres connected to opposite poles most axially (vertically) in the spindle. These distances are minimised for the quadrivalent as a whole only when it lies in two dimensions, i.e. in a plane parallel to the spindle axis. [ABSTRACT FROM AUTHOR]

Musculoskeletal movement results from muscle contractions, recoil of elastic tendons, aponeuroses, and ligaments, or combinations thereof. Muscular and elastic contributions can vary both across behaviors and with changes in temperature. Skeletal muscles reach peak contraction speed at a temperature optimum with performance declining away from that optimum by approximately 50% per 10°C, following the Q10 principle. Elastic recoil action, however, is less temperature sensitive. We subjected Axolotls (Ambystoma mexicanum) to changes from warm (23°C), via medium (14°C), to cold (6°C) temperature across most of their thermal tolerance range, and recorded jaw kinematics during feeding on crickets. We sought to determine if suction feeding strikes and food processing chews involve elastic mechanisms and, specifically, if muscular versus elastic contribution vary with temperature for gape opening and closing. Measurements of peak and mean speed for gape opening and closing during strikes and chews across temperature treatments were compared with Q10-based predictions. We found that strike gape speed decreased significantly from warm and medium to cold treatments, indicating low thermal robustness, and no performance-enhancement due to elastic recoil. For chews, peak, and mean gape closing speeds, as well as peak gape opening speed, also decreased significantly from warm to cold treatments. However, peak gape opening and closing speeds for chews showed performance-enhancement, consistent with a previously demonstrated presence of elastic action in the Axolotl jaw system. Our results add to a relatively small body of evidence suggesting that elastic recoil plays significant roles in aquatic vertebrate feeding systems, and in cyclic food processing mechanisms., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

Purpose: To study medical students' letters of recommendation (LORs) from their applications to medical school to determine whether these predicted medical school performance, because many researchers have questioned LORs' predictive validity., Method: A retrospective cohort study of three consecutive graduating classes (2007-2009) at the Uniformed Services University of the Health Sciences was performed. In each class, the 27 students who had been elected into the Alpha Omega Alpha (AOA) Honor Medical Society were defined as top graduates, and the 27 students with the lowest cumulative grade point average (GPA) were designated as "bottom of the class" graduates. For each student, the first three LORs (if available) in the application packet were independently coded by two blinded investigators using a comprehensive list of 76 characteristics. Each characteristic was compared with graduation status (top or bottom of the class), and those with statistical significance related to graduation status were inserted into a logistic regression model, with undergraduate GPA and Medical College Admission Test score included as control variables., Results: Four hundred thirty-seven LORs were included. Of 76 LOR characteristics, 7 were associated with graduation status (P ≤ .05), and 3 remained significant in the regression model. Being rated as "the best" among peers and having an employer or supervisor as the LOR author were associated with induction into AOA, whereas having nonpositive comments was associated with bottom of the class students., Conclusions: LORs have limited value to admission committees, as very few LOR characteristics predict how students perform during medical school.

Background and Objectives: Lifestyle factors influence medical specialty choice, but which specialties are perceived to have the best lifestyles is poorly described in scientific literature. The objective of the study was to determine the rating of specialties by lifestyle., Methods: All fourth-year US medical students with a Department of Defense service obligation who participated in the 2008/2009 military Match were invited to participate in a survey following the Match. The survey listed 18 specialties and asked students to rate the lifestyle of each one on a 9-point scale, and the mean score was used as the rating. Students also listed their specialty choice in the Match., Results: The response rate was 52%, as 418 of the 797 eligible students responded and provided a rating for at least nine of the 18 specialties. The four specialties rated highest for lifestyle (1--9, with 9 being highest) were dermatology (8.4), radiology (8.1), ophthalmology (8.0), and anesthesia (7.5). The four specialties rated lowest were orthopedics (4.0), neurosurgery (3.1), general surgery (2.6), and obstetrics-gynecology (2.5). Family medicine (5.7) was the top-rated primary care specialty, followed by pediatrics (5.3) and internal medicine (4.7). Students rated the lifestyle of their own specialty only slightly higher (range 0.02 to 1.8) than all other students., Conclusions: The R.O.A.D. specialties (radiology, ophthalmology, anesthesia, and dermatology) are the top specialties with respect to lifestyle as viewed by current students. Students perceive their own specialty's lifestyle realistically. Research determining why a specialty perceived as having a lower-rated lifestyle is acceptable to some students and not others is needed.

Background: Internal hernias (IHs) can complicate laparoscopic Roux-en-Y gastric bypass (LRYGB). A number of radiological investigations can be used in the diagnosis. These include plain X-rays, upper gastrointestinal (UGI) series, ultrasound, and computed tomography (CT) scanning. We present radiological findings in our series of 58 symptomatic internal hernias based on our 6-year experience (2000-2006) of 2,572 LRYGB patients., Methods: A retrospective chart review was performed of all patients undergoing LRYGB who developed symptomatic internal hernia requiring operative intervention between January 1, 2000 and September 15, 2006. Types of radiological tests performed and their results were recorded., Results: Fifty-eight symptomatic internal hernias were recorded, of which 56/58 (97%) underwent radiological investigation; 2/58 went directly to surgery. Of the 56 patients who underwent diagnostic imaging, 41 plain abdominal X-rays, 37 CT scans, 26 UGI series, and eight ultrasound scans were performed. Sixty-five percent of UGI series and 92% of CT scans had positive features diagnostic of internal hernia. Performing both CT and UGI series successfully diagnosed IH in 100% of cases. Subgroup analysis did not reveal any association between positive result of imaging test and type of internal hernia., Conclusion: CT scanning is the single most effective radiological investigation for diagnosing internal hernias post-LRYGB. In non-diagnostic cases, the addition of an upper GI series increases the diagnostic rate to 100%.

Background: Laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery is known to have a significant effect on obesity-related comorbidities such as hypertension curing it in some (50-70%) while improving control in others. Our aim was to observe the changes in blood pressure (BP) in a cohort of 100 patients followed prospectively for 1 year after LRYGB., Methods: BP measurements were recorded prospectively in 100 consecutive patients preoperatively and then postoperatively at weeks 1, 5, 9, and months 6 and 12. In order to reduce bias, three BP measurements were made by the same nurse at each office visit and the mean recorded. Pre- and postoperative usage of antihypertensive medication was also noted., Results: Eighty-nine women and 11 men underwent LRYGB and their BP monitored for 1 year. There was an 85% follow-up rate with mean % excess body weight loss of 60. Reductions in systolic (9 mmHg) and diastolic (7 mmHg) BP measurements were seen as early as week 1 postoperatively and maintained for the duration of the observation period (P < 0.05). Furthermore, postoperative usage of antihypertensive medication is reduced to a third of preoperative use., Conclusion: LRYGB is associated with an early reduction in BP and antihypertensive medication usage which is maintained at 1 year after surgery. This early impact on blood pressure occurs before any significant weight loss is achieved thereby suggesting a hormonal mechanism that may be involved for the changes observed.

Background: Partial small bowel obstruction can occur as a result of circumferential extrinsic compression of the Roux limb as it traverses the transverse mesocolic rent from thickened cicatrix formation in this area. The aim of this study is to examine the incidence of Roux limb compression with particular attention to the timing of presentation and associated weight loss in the setting of a university hospital in the United States., Methods: A retrospective chart review was performed of all patients undergoing laparoscopic Roux-en-Y gastric bypass who developed symptomatic small bowel obstruction requiring operative intervention from January 1, 2000 and September 15, 2006., Results: Of 2215 patients, 20 (.9%) developed symptomatic Roux limb compression. The mean time to presentation was 48 days after LRYGB. By this stage, the mean percentage of excess body weight loss was 29%. Of the 20 patients, 19 underwent an upper gastrointestinal contrast study, the results of which confirmed the diagnosis. In all cases, laparoscopic intervention was successful in freeing the constricted Roux limb by dividing the cicatrix formation between the Roux limb and mesocolic window. Switching from continuous to interrupted closure of the space between Roux limb and mesocolic window appeared to reduce the incidence of this complication (P<.05)., Conclusion: Narrowing at the transverse mesocolon rent is an uncommon cause of small bowel obstruction after retrocolic laparoscopic Roux-en-Y gastric bypass. Unlike internal hernias, which tend to occur later in the clinical course and are associated with significant weight loss, Roux limb obstruction occurs earlier after gastric bypass and is not associated with significant weight loss. Interrupted closure of the mesocolic window might reduce the risk of Roux compression.

Background: Internal hernias (IHs) can occur after laparoscopic Roux-en-Y gastric bypass (LRYGBP), perhaps because of a lack of adhesion formation at the cut edges of the mesentery and a cutting through of sutures with a decrease in fat from weight loss. In patients undergoing reoperation after LRYGBP, we observed that bioabsorbable glycolide copolymer staple-line reinforcement (SLR) placed to mitigate staple-line bleeding had evoked adhesiogenesis and tissue fusion at the mesentery edges; therefore, we investigated whether use of this material decreases post-LRYGBP IH rates., Methods: The records of the 43 patients (3%) in whom an IH developed during a mean follow-up time of 2 years in a series of 1,704 LRYGBP procedures were reviewed retrospectively., Results: The IHs were in the Peterson's space (n = 4), the enteroenterostomy (n = 17), or the transverse mesocolon (n = 22). The IH rate was significantly higher in patients who had suture closure of the mesenteric defects at LRYGBP than in those without formal closure of the defects but in whom SLR was applied to the edges of the cut mesentery (P = 0.01). The suture-closure and SLR groups had similar demographic, operative, and follow-up characteristics. When transverse mesocolic IHs were excluded from analysis, patients given SLR remained less likely to have an IH (P = 0.05)., Conclusion: Use of bioabsorbable polymer SLR may decrease the occurrence of IHs after LRYGBP. Additional studies of the effect of mesentery closure method on IH incidence after LRYGBP are warranted.

Background: Internal hernia is a known complication after gastric bypass, especially when performed laparoscopically. The aim of this study was to see when internal hernias occur in relation to weight loss and time course after surgery. Furthermore, we wish to examine the impact of Roux limb positioning ante- versus retrocolic and whether switching to running versus interrupted closure of the mesenteric defects created at surgery made any difference., Methods: A retrospective chart review was performed of all patients undergoing laparoscopic Roux-en-Y gastric bypass surgery (LRYGB) who developed symptomatic internal hernia requiring operative intervention between January 1, 2000 and September 15, 2006., Results: Fifty-four internal hernias occurred in 2,572 patients, an incidence of 2.1%. The site of internal hernias varied: 25 (1%), transverse mesocolon; 22 (0.8%), enteroenterostomy; 7 (0.3%), Peterson's space. The mean time to intervention for an internal hernia repair was 413 +/- 46 days and average % excess body weight loss (%EBWL) in this period was 59 +/- 3.3. Subgroup analysis demonstrates internal hernia incidence to be 2 in 357 (0.6%) in antecolic Roux versus 52 in 2,215 (2.4%) in retrocolic Roux limb (odds ratio = 4, P < 0.05). Continuous closure versus interrupted stitching of mesenteric defects does not seem to alter the incidence of internal hernias., Conclusion: This study demonstrates that the majority of internal hernias occur after a significant (>50%) EBWL. Furthermore, the antecolic approach is associated with a much reduced incidence of internal hernia.

The neuronal ceroid lipofuscinoses (NCL, Batten disease) are a group of inherited neurodegenerative storage diseases in children. Mutations in different genes underlie different forms. Subunit c of mitochondrial ATP synthase is specifically stored in autofluorescent bodies in most of them, including a form in sheep. Mature bodies are lysosomal but the initial site of storage is not known, nor is it known how this leads to the characteristic neurodegeneration. Neurons were cultured in serum-free medium from control and affected sheep fetuses at 90 days gestation. They showed positive microtubule-associated protein staining, developed neurites, and had typical neuron morphology. Time-dependent accumulation of subunit c and of fluorescent storage bodies was observed in affected cells by immunocytochemistry and confocal microscopy. A small number of autofluorescent bodies were apparent after 4 days in culture. After 10 days these bodies were more numerous, more intensely autofluorescent, and often larger in size. By 14 and 21 days many neurons were packed with autofluorescent material. These bodies were not seen in control cultures. Immunocytochemistry revealed subunit c-positive storage material only in affected neurons and not in affected glial cells. Confocal microscope analysis, using organelle-specific dyes, demonstrated colocalization of autofluorescent bodies with lysosomes, not with mitochondria. Survival rates of the affected cells were unaffected by the storage body accumulation over a 3-month period. These cultures can now be used to study the mechanism of subunit c accumulation and of neurodegeneration and to test therapeutic possibilities., (Copyright 1999 Academic Press.)

Cytochalasin D (CD) was applied to crane-fly spermatocytes at late diakinesis with the aim of perturbing actin structure and actin function, thereby testing the hypothesis that intranuclear chromosome movement during late diakinesis is actin-based. Isolated tests were incubated in a range of CD concentrations (2-100 microM) for 1 or 2 h. None of those treatments resulted in cessation of prophase movements in living cells. An immediate effect of 10-100 microM CD at late diakinesis was the formation of highly refractile, actin-containing cables within the nonchromosomal nucleoplasm. No such cables were observed in vehicle-treated control cells. CD treatments caused autosomal bivalents in unusually large numbers of spermatocytes to become aggregated into densely-packed clusters; for example, with 40 microM CD about 80% of late diakinesis spermatocytes had clustered autosomes, vs. about 25% clustering in untreated cells. We conclude from these data that the mechanism of chromosome positioning at the nuclear envelope is CD-sensitive. Rhodamine-conjugates of phalloidin and DNase I were used to assess the status of actin in untreated cells as well as the effect of CD on actin distribution. Differences in nucleoplasmic staining with phalloidin and DNase I conjugates suggest that nucleoplasm at late diakinesis contains actin in a nonfilamentous form.

Chromosome and granule movements in meiotic prophase and prometaphase have been studied by time-lapse cinemicrography in live spermatocytes of the house cricket, Acheta domesticus. Chromosome movements in prophase cells, up to one hour or more before breakdown of the nuclear envelope, are described. These movements are frequent but saltatory; are based mostly at chromosome ends but also at kinetochores; occur in very intimate association with the inside of the nuclear envelope; are directed towards and away from the extranuclear centres (centrioles); tend weakly to accumulate bivalents round the two centres and reach a velocity of 0.65 micron/sec. Saltatory movements in granules associated with extranuclear asters are remarkably similar to basic characteristics to the intranuclear chromosome movements. Surprisingly, the chromosome movements (and those granules) are reversably blocked by colcemid (but not lumi-colcemid), and yet occur in the apparent absence of an intranuclear envelope. However, kinetochore movements in very early prometaphase are similar in velocity and other respects to prophase movements; later prometaphase movements are clearly slower, and those of anaphase very much slower still. -The prophase movements suggest a two component model for motion: a non-microtubule, linear force producer together withrotubules with a skeletal, orientational role. Arguably, both these components are also necessary for chromosome movements in prometaphase and anaphase.

A new method is offered for combined living cell and electron-microscopic studies of spermatocytes (or other cells) which normally do not adhere to glass. The key step is micro-injection of glutaraldehyde near the target cell whenever desired during observation in life. Fixation begins and simultaneously the cell is stuck very firmly to the underlying coverslip. The method is easy and reliable: cells are almost never lost and are well preserved, except for membranes. The application of the method is illustrated by studies of micromanipulated grasshopper spermatocytes. A chromosome was detached from the spindle and placed in the cytoplasm. Before or after the beginning of chromosome movement back toward the spindle, the cell was fixed, sectioned and the manipulated chromosome observed in the electron microscope. If the detached chromosome had not moved by the time of fixation, no or only one or two microtubules were seen at its kinetochore, but if movement had occurred, a few microtubules were always present. The arrangement of these microtubules corresponded to the direction of movement, but they commonly were at an unusual angle relative to the kinetochore. The origin and role in chromosome movement of the microtubules seen near moving chromosomes far from the spindle is not yet established, but a speculation is offered. A goal for future work is the detailed analysis of the microtubules associated with individual moving chromosomes. Such an analysis is feasible because the moving chromosome is far removed from the confusing mass of spindle microtubules, and its value is enhanced because the direction of movement at the time of fixation is known.

The dynamic properties of the spindle, and published numerical data, argue that the differentiation of alternate-1 and alternate-2 orientations of an interchange quadrivalent is real and meaningful, contra Boussy (1982).