An anatomic study of the thickness of the occipital bone. Implications for occipitocervical instrumentation

STUDY DESIGN

The authors measured the thickness and quality of occipital bone regions to determine screw placement during occipitocervical fusion and described the projection of the posterior dural venous sinuses.

OBJECTIVE

This study provides anatomic data relevant to areas of screw placement into the occiput during occipitocervical fixation.

SUMMARY OF BACKGROUND DATA

Few reports exist regarding the morphometrics of the occipital bone and intracranial structures relevant to occipitocervical fusion.

METHOD

The thickness of the posterior inferior occipital bone was measured relative to a 10 x 5 cm grid. Sections were evaluated grossly and histologically. The projections of the posterior dural venous sinuses were determined by direct measurements.

RESULTS

The maximum thickness of the occipital bone, which ranged from 11.5 to 15.1 mm in males and from 9.7 to 12.0 mm in females, was at the level of the external occipital protuberance. The occipital bone was thicker than 8 mm in an area extending laterally from the external occipital protuberance for 23 mm and consisted of dense cortical bone with little or no diploic bone. The projection of most of the torcula on the external surface of the occipital bone was located superior to the center of the external occipital protuberance (mean, 12.6 mm superior and 4.7 mm inferior to external occipital protuberance), whereas that of the transverse sinus was distributed more evenly above and below the external occipital protuberance (mean, 7.3 mm superior and 6.5 mm inferior).

CONCLUSIONS

Screws that are 8-mm long may be inserted in the region of the superior nuchal line (Level 0) extending 2 cm laterally from the center of the external occipital protuberance, 1 cm from the midline at a level 1 cm inferior to the external occipital protuberance (Level 1), and 0.5 cm from the midline at a level 2 cm inferior to the external occipital protuberance (Level 2). The major dural venous sinuses are situated immediately beneath the thickest regions of the occiput and are at risk of penetrative injury during screw placement.

Percutaneous balloon compression of the trigeminal nerve for treatment of trigeminal neuralgia

The technique of percutaneous balloon compression for treatment of trigeminal neuralgia is demonstrated by using embedded audiovisual kernels. A text-based description with linked images is also provided to accomodate varying computer hardware capabilities. A new needle system for guiding the balloon catheter to the entrance of Meckel's cave and a balloon pressure monitoring system for the procedure is described and demonstrated. Results from a series of 141 consecutive patients treated during the period between 1983 and 1995 indicate an initial success rate of 92%. Fifty-seven percent of patients have postoperative numbness, which is described as mild to moderate by 94% of them. Sixteen percent have ipsilateral masseter-pterygoid weakness after compression. The overall recurrence rate is 26%. A Kaplan-Meier survival curve indicates that 60% of patients are pain free 8 years after surgery without recurrence requiring reoperation. The recurrence rate does not significantly differ from patients with first division pain to patients without first division involvement. An absent corneal reflex has not occurred, nor has anesthesia dolorosa. Balloon compression injures the myelinated fibers that mediate the “trigger” to the lancinating pain of trigeminal neuralgia. Because the corneal reflex is mediated by unmyelinated fibers, selective, monitored compression of myelinated fibers should preserve the corneal reflex when first division pain is present.

Fluorescence in situ hybridization analysis of renal oncocytoma reveals frequent loss of chromosomes Y and 1

PURPOSE

Cytogenetic studies of a small number of renal oncocytomas have indicated that loss of chromosomes 1 and Y may be involved in the pathogenesis of this tumor. To evaluate these observations further we selected paraffin embedded renal oncocytoma specimens from 20 male and 10 female patients for fluorescence in situ hybridization analysis.

MATERIALS AND METHODS

Isolated nuclei were prepared from paraffin embedded specimens, and fluorescence in situ hybridization was performed with enumeration probes for chromosomes 1, 12, X and Y.

RESULTS

Tumors from 10 male (50%) and 4 female (40%) patients demonstrated chromosomal alterations. Loss of chromosome Y was observed in specimens from all 10 male patients, and loss of chromosome 1 or gain of chromosome 12 was noted in 5 and 2 of these specimens, respectively. Of the 4 female patients with chromosomal abnormalities 2 had loss of chromosome 1, 1 had gain of chromosome 1 and 1 had gain of chromosome 12.

CONCLUSIONS

Our results confirm that loss of chromosomes Y and 1 is common in renal oncocytoma, and that the alterations are probably involved in the pathogenesis of this tumor.

Laparoscopic marsupialization of symptomatic polycystic kidney disease

PURPOSE

Although laparoscopic unroofing of simple renal cysts has proved to be an effective form of therapy, its use for treatment of multiple renal cysts or symptomatic autosomal dominant polycystic kidney disease only recently has been investigated.

MATERIALS AND METHODS

The results of laparoscopic marsupialization of symptomatic renal cysts in 13 patients was determined 12 to 28 months postoperatively by assessing subjective pain relief, and comparing preoperative and postoperative computerized tomography (CT). Eight patients had autosomal dominant polycystic kidney disease. Multiple dominant (more than 3 cm.) cysts were marsupialized in 11 patients and 1 dominant cyst was treated in 2.

RESULTS

Of 13 patients with symptomatic renal cysts and 8 with autosomal dominant polycystic kidney disease 8 (62%) and 4, respectively, were pain-free 12 to 28 months postoperatively. Two patients had persistent pain, while 3 had recurrent pain 7 to 16 months postoperatively. All 5 patients had persistent or recurrent dominant cysts on followup CT. Followup CT demonstrated resolution or a significant decrease of the largest and all or all but 1 of the other dominant cysts in 6 of 7 pain-free patients. Intraoperative ultrasound detected unidentified cysts during an open and laparoscopic procedure. No deleterious effects on serum creatinine were observed.

CONCLUSIONS

Laparoscopic marsupialization is a safe, relatively successful technique for providing persistent pain relief in patients with autosomal dominant polycystic kidney disease. Although the 2-year pain-free rate approaches the 62% rate reported for open surgical cyst resection, continued efforts to improve current laparoscopic techniques are clearly indicated. Persistence or recurrence of dominant cysts on CT correlated with persistent or recurrent symptoms. Intraoperative ultrasound is effective in identifying dominant cysts.

Self-reports on the Eating Disorder Inventory by female aerobic instructors

This study examined the possibility of eating disorders in 30 female aerobic dance instructors. All subjects completed a biographical questionnaire and the Eating Disorder Inventory. The results showed that the aerobic instructors yielded scores which were comparable to similarly aged female weight lifters but tended to be lower than those of women distance runners (also of similar age). Interestingly, 23% (n = 7) of the subjects reported a previous history of bulimia and 17% (n = 5) reported a previous history of anorexia. Thus, 40% of the instructors indicated a previous experience with eating disorders. Based on all 30 participants, the mean scores associated with Body Dissatisfaction, Drive for Thinness, Ineffectiveness, and Perfectionism were quite comparable to those previously established for anorexic groups. In addition, a relatively high percentage of the sample yielded scores which were actually greater than mean values associated with anorexia patients on nine of the 11 subscales. Based on these results, a number of the aerobic dance instructors possessed scores suggesting behaviors and attitudes consistent with female athletes whose sports emphasize leanness and comparable to those who have eating disorders.

Plasma prolactin, cortisol, and thyroid responses of the brown trout (Salmo trutta) exposed to lethal and sublethal aluminium in acidic soft waters

Brown trout, with indwelling dorsal aortic cannulae, were exposed to various concentrations of aluminium (Al; 50 micrograms liter-1, 100% mortality over 48 hr; 25 micrograms liter-1, 50% mortality over 120 hr; 12.5 micrograms liter-1, 0% mortality over 120 hr) in acidic (pH 5.0) soft water. The plasma concentrations of prolactin (PRL), cortisol, thyroxine (T4), and triiodothyronine (T3) were monitored. Plasma PRL concentrations were transiently depressed (to less than 20% of resting concentrations) after 12 hr in trout in the two highest water Al concentrations, but were unchanged in the trout exposed to 12.5 micrograms liter-1 Al. Plasma cortisol concentrations were elevated in response to all water Al levels and remained elevated in trout in the lethal conditions. The sublethally exposed trout showed a recovery in plasma cortisol concentrations by 120 hr. Plasma T4 concentrations were significantly elevated in trout exposed to both the lethal and the sublethal Al concentrations (from mean resting concentrations of 1-2 ng ml-1 to peaks of 8.9 and 9.0 ng ml-1 in the 50 and 12.5 micrograms liter-1 Al groups, respectively), although a recovery in plasma concentrations was evident in the sublethally exposed trout from 72 hr onwards. Plasma T3 concentrations were relatively stable in the trout exposed to the two highest doses of Al, whereas the trout under the lowest, sublethal, Al conditions exhibited a sustained (12-72 hr) elevation in plasma T3 concentrations (from a mean resting concentration of 0.9 ng ml-1 to a peak of 4.2 ng ml-1 at 48 hr). No clear relationship was apparent between the plasma PRL concentrations and the previously reported ionoregulatory status of the trout.

Axon and ganglion cell injury in rabbits after percutaneous trigeminal balloon compression

New Zealand white rabbits were used to determine whether the changes in the Vth cranial nerve sensory root after compression were associated with the loss of a specific subclass of Vth cranial nerve ganglion cells, the disappearance of a distinct subset of primary afferent terminals in Vth cranial nerve nucleus caudalis, and/or injury to a specific axonal fiber type. There was no significant difference in the size of surviving ganglion cells after Vth cranial nerve compression, as measured 2 to 3 months after injury (P > 0.5, n = 4). Densitometric analysis of the nerves of rabbits that survived > 2 months after compression showed no significant difference in the immunoreactivity of substance P and calcitonin gene-reactive protein between compressed and control sides (P > 0.1, n = 4). Fink-Heimer staining of the Vth cranial nerve subnucleus caudalis revealed that transganglionic degeneration was most dense in the deeper layers, which are the sites of termination of large myelinated fibers. Ultrastructural evaluation of the type of myelinated axons injured by Vth cranial nerve compression in rabbits killed 7, 14, 37, and 270 days after injury was studied, and morphometric analysis was performed. The frequency distribution of axon diameters was significantly different for injured and control areas. The injured areas had higher ratios of small (< 3-microns diameter) to large-diameter axons compared to control distribution. These data indicate that balloon compression results in loss of fibers from the Vth cranial nerve sensory root and extensive transganglionic degeneration in the Vth cranial nerve brain stem complex. Cell size measurements and immunocytochemical data suggest that there is no specific loss of small ganglion cells or fine-caliber primary afferents. These experiments suggest that balloon compression relieves trigeminal pain by injuring the myelinated axons involved in the sensory trigger to the pain.

The physiological effects of bench/step exercise

Recent investigation of acute cardiorespiratory responses to the current 'popularised' style of bench/step exercise has validated its use in improving aerobic physical fitness, particularly in women. However, no marked differences in relative measures of cardiorespiratory demand have been reported between men and women. Instructor data and training investigations further substantiate the effectiveness of bench/step exercise in promoting physical fitness, including upper body strength. However, the energy cost of bench/step exercise can vary dramatically. Important factors include, the selected step height, exercise rate, imposed step manoeuvre, routine format and use of hand-held weights. Hand-held weights may be more useful for men than woman. During training, bench/step exercise has been reported to yield a high incidence of grade I injury complaints, particularly in the calf and shoulder region. However, nearly 90% of these complaints were attributable to acute muscle soreness. Few serious injuries have been associated with the activity. Biomechanical research has shown that the ground reaction forces (GRF) experienced during bench stepping are lower than running and directly related to the step height and type of manoeuvre. In addition, compared with novices, instructors exhibit a moderation in the GRF pattern generated during landing. This suggests that a learning effect has occurred and that teachers yield a more consistent landing pattern. Finally, the activity may be effective in improving body composition, but a consideration of factors related to energy expenditure (e.g. exercise duration and dietary control) appear to be important in regimens prescribed for modifying body fat.

In vivo metabolic response of glucose to dichloroacetate in humans

Hyperglycemia is common in severely ill patients and is related principally to an increase in glucose production. Dichloroacetate (DCA), which is known to increase the rate of pyruvate oxidation, has been shown to lower plasma glucose concentrations in normal fasting subjects and in diabetics and thus may be efficacious in treating stress induced hyperglycemia. However, the mechanism by which DCA lowers the plasma glucose concentration in humans has not been elucidated. To examine the human in vivo metabolic alterations induced by DCA, six fasting volunteers were infused with 6,6-D2-glucose and indirect calorimetry was performed prior to and following DCA administration. Glucose, lactate, and alanine net balance across the leg were also quantitated. Following DCA administration, plasma glucose concentrations decreased by 9% due to a proportional decrease in the rate of glucose production (P < 0.05). DCA had no affect on glucose clearance or leg net balance; however, the rate of glucose oxidation increased by 24% from baseline (P < 0.05). This increase in glucose oxidation without a compensatory change in peripheral glucose consumption suggests an improved efficiency in peripheral glucose utilization induced by DCA. Plasma concentrations of lactate and alanine were also lowered by DCA (56% for lactate, 66% for alanine, P < 0.05) without a significant alteration in leg net balance. These results suggest that DCA may decrease gluconeogenesis by limiting the availability of the precursor substrates lactate and alanine. Thus dichloroacetate may be an appropriate alternative to insulin in correcting mild elevations in plasma glucose concentrations. Furthermore, DCA may be especially effective in severely ill patients where hyperglycemia is largely due to increases in gluconeogenesis.

Lipid and lipoprotein changes in women following 6 months of exercise training in a worksite fitness program

It was the purpose of this investigation to examine the influence of a worksite aerobic training program on serum lipid and lipoproteins and cardiovascular fitness in female employees. Thirty-seven healthy but previously untrained, female employees (Ss) from Westinghouse Corporation, (College Station, Texas) volunteered for the study. Ss were randomly assigned to either an exercise group (Ex) (n = 20) or control group (C) (n = 17). Prior to training (PRE) and following training (POST), all Ss were measured for weight (WT), body composition (%FAT) and tested for maximal oxygen consumption (VO2 max). PRE and POST Lipid analysis included: total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and triglycerides (TG). Following PRE testing, the Ex group aerobically trained by walking, jogging and/or cycling, at least 3 days per wk for 24 wks. Exercise training resulted in an improvement in VO2 max (p < 0.0006) and a 2 kg WT loss in Ex (p < 0.025) with no change in C. Both Ex and C Ss exhibited a loss in %-FAT (p < 0.0001), and a decrease in TC (p < 0.0001) and LDL-C (p < 0.0001). No differences were observed between groups or over the training period for VLDL-C or TG. Although HDL-C increased 6 mg/dl in the Ex group but not in C, this difference did not reach statistical significance (p < 0.0625). These results demonstrate that aerobic training by females in a worksite fitness program significantly improves cardiovascular fitness without altering lipids or lipoproteins.

Regulation of the E beta gene in vivo: lessons from E beta d transgenic mice

We have examined the expression and regulation of the MHC class II E beta d gene in both cell lines and in transgenic mice. In transient transfection assays, as little as 192 bp of the E beta d proximal promoter was sufficient to direct constitutive expression of a reporter gene in a B cell line and to confer inducibility by IFN-gamma in a macrophage cell line. To determine if the same E beta d promoter sequences were also sufficient to direct correct expression in vivo, E beta d transgenes bearing either 4.1 or 0.2 kb of upstream sequence were introduced into an inbred mouse strain with a non-expressed endogenous E beta gene. Expression of both transgenes mirrored the expression of the endogenous I-A protein in thymus, B cells and macrophages with regard to both constitutive and cytokine-inducible expression. These results indicate that for the E beta gene only 200 bp of proximal promoter sequence are required to achieve tissue-specific and cytokine-inducible expression. This is in striking contrast to the E alpha gene, the only other murine class II gene whose promoter has been analyzed in vivo, which has been shown to require 2.0 kb of upstream sequence for appropriate expression. These data demonstrate, therefore, that the location of critical regulatory elements for the E beta and E alpha genes may differ.

Aneusomies of chromosomes 8 and Y detected by fluorescence in situ hybridization are prognostic markers for pathological stage C (pt3N0M0) prostate carcinoma

In an attempt to identify new prognostic markers, we performed fluorescence in situ hybridization (FISH) ploidy analysis of tumor tissue from patients with a targeted stage and histological grade of prostate carcinoma. We identified all 227 patients from the Mayo Clinic radical prostatectomy data base who had a high histological grade pathological stage C (pT3N0M0) tumor removed between 1966 and 1987. After histological review of the paraffin-embedded specimen blocks, 181 cases were suitable for FISH analysis using chromosome enumeration probes for chromosomes 7, 8, 10, 12, X, and Y. FISH detected 80 (44%) diploid, 22 (12%) tetraploid, and 79 (44%) aneuploid tumors. The common aneusomies were of chromosomes 7 and 8, which were present in 51 (28%) and 46 (25%) tumors, respectively. Aneusomies of chromosomes 10, 12, X, and Y were observed in 11 (6%), 15 (8%) 12 (7%) and 16 (9%) tumors, respectively. FISH aneuploid tumors showed a trend of more frequent systemic prostate cancer progression than nonaneuploid tumors (P = 0.060). For individual chromosome anomalies, gains of chromosome 8, aneusomy of chromosome 8, and aneusomy of chromosome Y correlated highly with systemic cancer progression (P = 0.006, 0.013, and 0.021, respectively). Gains of chromosome Y and aneusomy of chromosome Y were associated with an increased prostate cancer death rate (P < 0.001 for both). Multivariate analysis showed that gains of chromosome 8 and aneusomy of chromosome Y were significant independent "predictors" of systemic cancer progression (P = 0.008) and cancer death (P < 0.001), respectively. These results demonstrate that aneuploidy and specific aneusomies detected by FISH are potential markers for a poor prognosis in histological high-grade pathological stage C (pT3N0M0) prostate carcinoma.

Teaching efficacy of a medical education module on genetic testing for cancer

BACKGROUND

With the identification of the breast cancer susceptibility genes BRCA1 and BRCA2, clinical testing for detection of the mutated genes may be available in the near future. Primary care physicians increasingly serve as full-service providers and gatekeepers and must be aware of presymptomatic testing in order to counsel their patients appropriately. To address this educational need, a new module was incorporated into the genetics course taken by first-year medical students at the Medical College of Virginia.

METHODS

The module used small groups, led by genetics faculty and members of the Virginia Breast Cancer Foundation, for discussion of case examples. The medical students' knowledge of and attitudes toward cancer and predictive genetic testing were assessed by a pretest and a posttest.

RESULTS

After the module, knowledge scores increased by 27%, and significant changes were seen in the students' attitudes toward issues such as the regulation of testing availability and the psychological effect of testing. Most students consistently felt that predictive genetic testing is beneficial, that they would have the testing themselves, that genetic counseling should be required for testing, and that insurers' access to genetic testing results should be limited. Overall, the module was received favorably by all participants.

CONCLUSIONS

Small-group discussion of relevant case examples increases knowledge and awareness of issues regarding presymptomatic genetic testing for breast cancer.

Vulnerability of vertebral artery in anterolateral decompression for cervical spondylosis

This study aimed to provide anatomic data for the location of the vertebral artery and offer an optimal approach for lateral cervical decompression that minimizes the risk of injury to the vertebral artery. Anatomically, there has been little study documenting the safe zone to prevent vertebral artery injury during the resection of the uncinate process or uncovertebral joint during the lateral decompression of the nerve root. The transverse foramen and its related parameters were measured on dry cervical spines from C3 to C7. The cadaveric cervical spines were dissected to determine a method for resection of the uncovertebral joint with decreased risk of vertebral artery laceration. The anteroposterior diameters of the transverse foramina gradually decreased from C6 to C3. The transverse diameters of the transverse foramina were smaller at C5. The interforaminal distance, width of the vertebrae, interuncinate distance, and the distance from the lateral tip of the uncinate process to the medial border of the transverse foramen became smaller in more cephalad vertebrae. After subtotal vertebrectomy and opening of the anterior walls of the transverse foramina, the resection of the uncovertebral joint and lateral decompression became easier and safer. Anatomic measurements obtained in this study indicate the vertebral artery to be at risk during decompression of the more cephalad vertebrae. The lateral decompression can be completed under direct vision with smaller rongeurs and curettes, rather than with high speed burr after deroofing the anterior walls of transverse foramina and retracting the vertebral artery laterally.

The release of glutamate and aspartate from rat brain synaptosomes in response to domoic acid (amnesic shellfish toxin) and kainic acid

Kainic acid is known to stimulate the release of glutamate (GLU) and aspartate (ASP) from presynaptic neurons. It has been suggested that the enhanced release of these endogenous EAA's plays a significant role in the excitotoxic effects of KA. Domoic acid (DOM), a shellfish toxin, is structurally similar to KA, and has been shown to be 3-8 times more toxic than KA. In this study, effects of KA and DOM on the release of GLU and ASP from rat brain synaptosomes were investigated. Amino acid analysis was performed by the reversed phase HPLC, following derivatization with 9-fluorenylmethyl chloroformate (FMOC). Potassium chloride (40 mM) was used as a positive control, and stimulated GLU release from rat brain synaptosomes in presence or absence of Ca2+. DOM enhanced the release of GLU, whereas KA stimulated the release of both GLU and ASP from synaptosomes in the presence of Ca2+. However, their potency to stimulate GLU and ASP release was enhanced in absence of Ca2+. These results indicate that different mechanisms may be involved in the release of GLU and ASP in response to DOM and KA, and that neurotransmitter release appeared to be highly specific for these agonists. It would appear that DOM and KA may interact with different receptors on the presynaptic nerve terminal, and/or activate different subtypes of voltage-dependent Ca2+ channels to promote influx of Ca2+ which is targeted for different pools neurotransmitters.

Glomerular actions of arginine vasotocin in the in situ perfused trout kidney

Recent measurements of plasma arginine vasotocin (AVT) in teleost fish suggest circulating concentrations of 10(-10)-10(-12)M. Previous studies of the renal actions of AVT in vivo suggest both diuretic and antidiuretic effects, but at unknown circulating concentrations. We have investigated the renal actions of 10(-9) and 10(-11) M AVT in vitro using an in situ perfused kidney preparation of rainbow trout (oncorhynchus mykiss). AVT increased vascular resistance (56%), reduced perfusate flow (P < 0.001), and increased interrenal aortic pressure (P < 0.001). AVT resulted in dose-dependent decreases in urine flow rates, glomerular filtration rates, and tubular transport maxima for glucose. AVT at 10(-11) M reduced relative free water clearances (P < 0.01), but urine/plasma inulin ratios were unchanged, whereas 10(-9)M AVT reduced urine/plasma inulin ratios (P < 0.01) and increased relative free water clearances (P < 0.05). The filtering population of glomeruli was reduced by both 10(-11) and 10(-9)M AVT to approximately one-third of the glomeruli, and a similar population of arterially perfused but nonfiltering glomeruli emerged. These results demonstrate that physiological concentrations of AVT have potent glomerular antidiuretic action in the trout, reducing the number of functional glomeruli, and imply reduced individual nephron filtration rates.

Activation of class II MHC genes requires both the X box region and the class II transactivator (CIITA)

CIITA, a gene that can complement a transcriptional mutation of the major histocompatibility complex (MHC) class II genes, was tested for its ability to function as a coactivator, CIITA cDNA clones isolated showed alternative RNA splicing, but only one splice site combination was able to restore class II MHC gene expression. DNA-mediated transfection experiments showed that CIITA directs its activity through the X box element; the presence of CIITA leads to the formation of a higher order complex at the X box region; and CIITA contains a potent activation domain. These findings support the hypothesis that CIITA directly interacts with the MHC class II-specific transcription factors and is required for expression.

Posterior plating of the cervical spine

A retrospective review of 36 patients treated with posterior cervical plating and autogenous iliac crest bone graft was performed to evaluate the results of posterior cervical plating in terms of fusion, outcome, technique, and complications. Numerous methods of cervical stabilization have been described with varying fusion rates and complications. Compared to wiring techniques, there is little information concerning the results of posterior cervical plating. Thirty-six patients with cervical instability underwent posterior plating with lateral mass screw fixation. Twenty-two had acute traumatic instability, four had late traumatic instability, six had metastatic disease, and four had postlaminectomy spondylotic instability. A Minerva brace was worn postoperatively for 3 months and fusion was assessed by bone incorporation on plain films, stable dynamic flexion-extension views, and absence of neck pain. Postoperative MRI and CT imaging was assessed in those patients who underwent these modalities. Fusion occurred at an average of 3 months in all patients. One patient demonstrated postoperative neurologic deterioration, but this resolved with subsequent decompression. Six patients had loosening of short, unicortical screws, but this did not affect the fusion result in five of these patients. The use of titanium implants allowed operative CT and MR imaging without the excessive artifact associated with stainless steel implants. Posterior cervical plating with lateral mass fixation and bone grafting offers a reliable method of achieving fusion. Bicortical lateral mass screws are less likely to loosen than unicortical screws, and no major complications occurred.

A mutation in the Schizosaccharomyces pombe rae1 gene causes defects in poly(A)+ RNA export and in the cytoskeleton

A collection of fission yeast Schizosaccharomyces pombe conditional mutants was screened for defective nucleocytoplasmic transport of poly(A)+ RNA by fluorescence in situ hybridization. We identified a temperature-sensitive mutant that accumulated poly(A)+ RNA in the nucleus and have named it rae1-1, for ribonucleic acid export. All rae1-1 cells exhibit the defect in poly(A)+ RNA export within 30 min following a shift to the non-permissive temperature. In addition, in the rae1-1 mutant, actin and tubulin become disorganized, and cells undergo an irreversible cycle arrest. Results from experiments in which rae1-1 cells were arrested in various phases of the cell division cycle and then shifted to nonpermissive temperature suggest that cells are particularly vulnerable to loss of rae1 function during G2/M. However, the inability to export RNA from the nucleus to the cytoplasm was not limited to a particular phase of the cell division cycle. The rae1 gene was isolated by complementation and encodes a predicted protein of 352 amino acids with four beta-transducin/WD40 repeats.

B7-1 and B7-2 costimulatory molecules activate differentially the Th1/Th2 developmental pathways: application to autoimmune disease therapy

CD4 T helper precursor cells mature along two alternative pathways, Th1 and Th2. Here we show that these pathways are differentially activated by two costimulatory molecules, B7-1 and B7-2. Using anti-B7 antibodies, this developmental step was manipulated both in vitro and in vivo in experimental allergic encephalomyelitis (EAE). Anti-B7-1 reduced the incidence of disease while anti-B7-2 increased disease severity. Neither antibody affected overall T cell induction but rather altered cytokine profile. Administration of anti-B7-1 at immunization resulted in predominant generation of Th2 clones whose transfer both prevented induction of EAE and abrogated established disease. Since co-treatment with anti-IL-4 antibody prevented disease amelioration, costimulatory molecules may directly affect initial cytokine secretion. Thus, interaction of B7-1 and B7-2 with shared counterreceptors CD28 and CTLA-4 results in very different outcomes in clinical disease by influencing commitment of precursors to a Th1 or Th2 lineage.