Progress in understanding the Drosophila dnc locus

The genetic dissection of learning and memory in Drosophila is two decades old. Recently, a great deal of progress has been made towards isolating new mutants as well as towards a better understanding of the originally isolated ones. This paper reviews the recent developments in the understanding of the structure and function of the gene identified by the first and best-characterized of these mutants, the Drosophila dunce mutant.

Two-versus three-sample method for estimating gentamicin pharmacokinetic values

The performances of two-sample and three-sample methods for estimating gentamicin pharmacokinetic values were studied. The medical records of patients who had received a gentamicin dosage consultation at a Veterans Affairs medical center between June 1989 and May 1991 were reviewed. For each patient, the pharmacokinetics service had prospectively used three serum gentamicin concentrations (SGCs) determined from three blood samples taken during an initial gentamicin regimen to estimate gentamicin pharmacokinetic values and determine the alternative would achieve the desired SGCs. In the two-sample method, the authors retrospectively used the initial peak and trough SGCs determined from two blood samples to estimate pharmacokinetic values and establish an alternative regimen. The two methods were evaluated by comparing their results with each other and with the actual pharmacokinetic values determined from SGCs measured during the subsequent gentamicin regimen. A total of 27 patients (all men; mean age, 62 years) were included in the study. The two-sample and three-sample methods differed significantly in their estimates of elimination rate constant and half-life but not clearance, volume of distribution, or the daily dose needed to achieve the intended SGCs. Neither method produced estimates that differed significantly from the actual pharmacokinetic values. The three-sample method was less biased than the two-sample method in the prediction of trough SGCs. In middle-aged and elderly men, a two-sample method and a three-sample method of estimating gentamicin pharmacokinetics differed significantly only in the prediction of trough SGCs. The difference was probably not clinically important.

Intracranial meningiomas of the first two decades of life

Meningiomas arising in the first two decades of life are uncommon and their characteristics are controversial. Some authors believe meningiomas in younger patients occur in different locations, have more malignant histological features, and have a worse prognosis than those in adults. To address this controversy, the authors retrospectively reviewed 23 cases of meningiomas in patients under 21 years of age at diagnosis who were operated on at the University of Turin (1948 to 1990) or at the University of California, San Francisco (1970 to 1989). These tumors represented 2.9% of all tumors in this age group and 1.8% of all meningiomas during the study period at the two institutions. There were 14 males and nine females. The mean age at surgery was 13.3 +/- 5.6 years; nine cases occurred in the first decade and 14 in the second. The most common neurological symptoms were a focal neurological deficit (33%) and seizures (25%). Seventy percent of the tumors were supratentorial. A gross total resection was performed in 60% of the cases. Histologically, the majority (74%) of the tumors were meningothelial or mixed. An increased number of mitoses was observed in 33% of the tumors, focal necrosis in 29%, and invasion of adjacent brain in 14%; however, none of the tumors was classified as a Grade III (anaplastic) meningioma. All patients are alive without evidence of recurrent disease 3 to 22 years (mean +/- standard deviation: 10 +/- 7.3 years) after surgery. This study confirms the rarity of meningiomas of the first two decades of life and the absence of the female predominance associated with meningiomas in adults. The location and histological features of these tumors are similar to those in adults; they have a low recurrence rate, and the outcome and survival rate are excellent.

Proliferative potential and prognostic evaluation of low-grade astrocytomas

Despite their histological similarity, low-grade astrocytomas vary widely in their clinical behavior. To elucidate this variable behavior, we measured the proliferative potential of 69 primary and 18 recurrent low-grade astrocytomas and correlated the results with the clinical characteristics and outcome. Each patient received an intravenous infusion of bromodeoxyuridine (BUdR); BUdR-labeled nuclei in excised tumor specimens were identified by immunoperoxidase staining. The BUdR labeling index (LI), or S-phase fraction, ranged from < 1 to 9.3%; the LI was < 1% in 64 (74%) patients and > or = 1% in 23 patients (26%). The LI did not appear to be associated with age, sex, tumor location, or whether the tumor was primary or recurrent. A Cox proportional-hazards analysis of the influence of the LI and other variables (age, sex, tumor location, extent of surgery, primary versus recurrent tumor) on survival showed that the LI and extent of surgery (total resection, subtotal resection, biopsy) were significant in predicting both survival and progression-free survival for all patients and for patients with primary tumors. The LI was also significant in predicting progression-free survival for patients with recurrent tumors. The correlation between the BUdR LI and both survival and time to recurrence suggests that the outcome of low-grade astrocytomas varies according to the proliferative potential. The growth rate of these histologically similar tumors should be assessed individually in order to select specific treatment.

Hepatitis following treatments with famotidine and then cimetidine

OBJECTIVE

To report a case of hepatitis induced by two histamine (H2)-receptor blockers, famotidine and cimetidine.

CASE SUMMARY

A 51-year-old obese woman with a duodenal ulcer developed symptomatic, famotidine-induced hepatitis. Other causes for hepatitis were ruled out. Famotidine was discontinued and the patient took omeprazole for a month without incident. Cimetidine therapy was then initiated and shortly thereafter, the patient developed another episode of symptomatic hepatitis that resolved upon drug discontinuation. Two abdominal ultrasound examinations six months apart and an abdominal computed tomography scan obtained later showed what appeared to be a stable, fatty liver.

DISCUSSION

This appears to be the first reported case of clinical hepatitis related to famotidine and the first reported case where clinical hepatitis followed the administration of two different H2-receptor blockers. The fatty liver probably was secondary to obesity and incidental to the hepatitis episodes.

CONCLUSIONS

Famotidine can cause clinical hepatitis, and drug-induced hepatitis can occur after the administration of two different H2-receptor blockers.

Microtubule aggregates in a clival chordoma

We report a case of a clival chordoma in a 21-year-old man that ultrastructurally demonstrated large numbers of microtubule aggregates within the rough endoplasmic reticulum. Histologically, the tumor demonstrated classic chordoma architecture characterized by numerous physaliphorous cells and an abundant extracellular matrix. The tumor cells stained strongly for cytokeratin, S100 protein, and epithelial membrane antigen, indicative of the epithelial origin of this tumor. Ultrastructurally, the most conspicuous feature of this tumor consisted of parallel bundles of criss-crossing microtubules within the rough endoplasmic reticulum. These microtubules had a diameter of approximately 27 nm and did not demonstrate an internal structure. To our knowledge, this is the first report of microtubule aggregates in a spheno-occipital chordoma. We note that microtubule aggregates have been described in a number of different entities, and though proposed as a specific feature of "chondroid chordoma," they are a nonspecific finding.

Preferential expression in mushroom bodies of the catalytic subunit of protein kinase A and its role in learning and memory

Involvement of the cAMP cascade in Drosophila learning and memory is suggested by the aberrant behavioral phenotypes of the mutants dunce (cAMP phosphodiesterase) and rutabaga (adenylyl cyclase). Line DCO581, isolated via an enhancer detector screen for genes preferentially expressed in the mushroom bodies, contains a transposon in the first exon of the catalytic subunit gene (DCO) of protein kinase A (PKA). RNA in situ hybridization and immunohistochemistry show that DCO is preferentially expressed in the mushroom bodies. The DCO581 insertion and an independently isolated hypomorphic allele (DCOB10) each produce homozygous lethality and a 40% decrease in PKA activity in heterozygotes. This decrease has mild effects on learning but no effect on memory. However, the 80% reduction in activity obtained by constructing heteroallelic yet viable DCO581/DCOB10 animals results in a dramatic learning and memory deficit. These results suggest that PKA plays a crucial role in the cAMP cascade in mushroom bodies to mediate learning and memory processes.

Idiopathic hypertrophic cranial pachymeningitis. Report of three cases

Hypertrophic cranial pachymeningitis is a rare, idiopathic form of granulomatous pachymeningitis. This report describes three cases of hypertrophic cranial pachymeningitis and discusses the clinical, radiographic, and pathological findings in these and other reported cases. These lesions typically cause progressive cranial nerve palsies, headaches, and cerebellar dysfunction. They occur in patients of all age groups; the peak incidence is in the sixth decade. Hypertrophic cranial pachymeningitis is best identified by magnetic resonance imaging. The diagnosis is established by excluding all other granulomatous and infectious diseases. A dural biopsy is essential to confirm the diagnosis. Hypertrophic cranial pachymeningitis is initially responsive to steroid therapy, but in most cases it recurs or progresses despite treatment. Surgical excision of granulomas is occasionally necessary to alleviate a mass effect. The long-term outcome remains uncertain for most patients, but progressive disease is usually fatal owing to cranial neuropathies.

Cluster of testicular cancer in police officers exposed to hand-held radar

Within a cohort of 340 police officers, six incident cases of testicular cancer occurred between 1979 and 1991 (O/E 6.9; p < 0.001, Poisson distribution). Occupational use of hand-held radar was the only shared risk factor among all six officers, and all routinely held the radar gun directly in close proximity to their testicles. Health effects of occupational radar use have not been widely studied, and further research into a possible association with testicular cancer is warranted.

Gangliogliomas: a clinicopathological study of 25 cases and review of the literature

The histopathological, clinical, and radiological findings in 25 patients (median age 20.5 years; range 1.7-64.2 years) with gangliogliomas were assessed to correlate degree of astrocytic anaplasia and proliferative potential with recurrence or survival. Most patients (64%) presented with seizures (median Karnofsky Performance Score 90%; range 70-100%). Computerized tomography and magnetic resonance imaging showed nonspecific abnormalities. Neoplastic ganglion cells were defined as heterotopic, irregularly grouped, or having more than one nucleus of bizarre shape or size. The astrocytic component was moderately anaplastic in 15 cases and highly anaplastic (HAA) in 10. Eight patients had gross total resection, 11 had subtotal resection, and six underwent biopsy. Ten patients (five gross total resection, three subtotal resection, two biopsy) had no further treatment, 15 underwent external irradiation, and five had adjuvant chemotherapy. Twenty-four patients are alive 15-394 weeks (median 203.5 weeks) postoperatively; one with ganglioglioma-HAA died at 65 weeks. No tumor recurred after gross total resection. Duration of preoperative symptoms < 1 year, greater anaplasia, and age > 30 years at diagnosis may have increased the risk of recurrence after subtotal resection or biopsy by four, three, and two times, respectively (not significant). Bromodeoxyuridine labeling index (BUdR LI) was < 1% in eight non-recurring tumors and 1.3% in another recurring twice (second recurrence LI = 1.6%). Most patients with ganglioglioma have a good prognosis. After gross total resection, only observation is required. After subtotal resection or biopsy, recurrence is possible. BUdR labeling may guide further therapy.

Genetic dissection of the learning/memory gene dunce of Drosophila melanogaster

The dunce (dnc) gene of Drosophila melanogaster codes for cAMP phosphodiesterase (PDE) and is required for normal learning/memory and for female fertility. The expression of the gene is elevated in mushroom bodies, brain structures implicated in olfactory learning and memory. In this study several chromosomal deletions and inversions that remove increasingly larger portions of the dnc gene from its 5' end and progressively more of the five known transcription start sites (tss) were used to assess the functions of the various transcriptional units. Surprisingly, the dnc PDE activity, female fertility, mushroom body expression, learning, and memory were unaffected by the removal of tss1 and tss2. tss3 was required for elevated mushroom body expression but not for female fertility nor initial learning. tss4 contributed to learning and the female fertility function, whereas tss5 contributed to female fertility. The results indicate that the structural complexity of the gene is of biological significance, with individual transcriptional units serving different biological functions.

Loss of heterozygosity for loci on chromosome 10 is associated with morphologically malignant meningioma progression

Meningioma is a common tumor of the central nervous system which displays morphological heterogeneity. In order to determine whether this phenotypic variability is associated with distinct or overlapping genetic lesions, we compared genotypes at several loci defined by allele length polymorphism in tumor and normal tissues from patients with meningioma. In particular, we concentrated on loci on chromosomes 22 and 10 because these genomic regions have previously been shown to be altered in the former in sporadic and familial meningiomas and in the latter as a late stage event in progression of another common brain tumor, astrocytoma. We examined 38 tumors which were classified as benign, atypical, or malignant by morphological criteria, invasive characteristics, or both. We found that loss of heterozygosity (LOH) for loci on chromosome 22 occurred in 5 of 15 benign, 2 of 2 atypical, and 5 of 10 malignant meningiomas. Similar alterations of chromosome 10 were found in 0 of 20 benign, 1 of 2 atypical, and 4 of 13 malignant meningiomas. Among the malignant tumors, LOH for loci on chromosome 10 occurred in 2 of 4 morphologically malignant tumors and in 2 of 4 morphologically and invasively malignant tumors. In contrast, LOH was not observed for any of the 5 informative tumors classified as malignant by invasive characteristics only. LOH for loci on chromosome 22 accompanied (but was not restricted to) allelic loss of loci on chromosome 10. These data suggest that the progression of meningiomas from arachnoidal cells to the morphologically malignant phenotype may, in part, entail the loss of a tumor suppressor gene(s) on chromosome 22 early in the process and that this may be compounded by alterations of chromosome 10, the LOH of which is associated with morphological signs of malignancy.

A new method for analyzing the cell kinetics of human brain tumors by double labeling with bromodeoxyuridine in situ and with iododeoxyuridine in vitro

BACKGROUND

Cell kinetics studies performed with immunohistochemical techniques to estimate the S-phase fraction have elucidated the proliferative potential of individual brain tumors.

METHODS

The authors developed a new double-labeling method that enables other cell kinetics variables, including the duration of the S-phase (Ts) and the potential doubling time (Tp), to be measured from a single biopsy specimen. Using this method, 100 brain tumors were labeled with bromodeoxyuridine (BUdR) in situ and with iododeoxyuridine in vitro; labeled cells were identified by double staining with immunogold-silver and alkaline phosphatase techniques.

RESULTS

Ts was fairly uniform (mean, 9.2 +/- 2.1 hour [+/- standard deviation]); range, 6.0-13.7 hours), but Tp varied from 1 day to more than 2 months. The Tp values correlated closely with the BUdR labeling index (LI), or S-phase fraction, and can be calculated from the equation: Tp = 26.9/LI1.02 (r = 0.98, P < 0.005).

CONCLUSIONS

This new method facilitates the quantitation of the proliferative potential of individual brain tumors. The S-phase fraction, Ts, and Tp can be calculated from analysis of a single biopsy specimen. This method can be used to estimate the prognosis of individual patients with brain tumors and to select treatment modalities more directly than is possible with single-labeling studies with BUdR.

Monitoring of clinical trials and interim analyses from a drug sponsor's point of view

This paper illustrates aspects of data monitoring of clinical trials in the pharmaceutical industry. Formal interim analyses are performed at least in part to address the question of whether the trial should proceed or whether there should be an early termination of the trial. For formal interim analyses, frequently independent data and safety monitoring committees are utilized for monitoring clinical trials, and adjustments to nominal significance levels for test statistics are required. Various statistical methods developed during the last fifteen years are utilized. Administrative interim analyses are those analyses that are performed without any intention to stop the trial as a consequence of those analyses. For administrative interim analyses, adjustments to significance levels may not be required, but results must still be carefully interpreted. Regardless of the interim analyses performed, it is critical that the plans for interim analyses be identified in the study protocol, and the dissemination of interim results be carefully restricted. The following clinical trials sponsored by Merck Sharp and Dohme Research Laboratories (MSDRL) will illustrate these points: CONSENSUS; CONSENSUS II; 4S; Haemophilus influenza type b efficacy trial; famotidine in upper gastrointestinal haemorrhage, and a phase II analgesic study. It is anticipated that data monitoring and interim analysis activities will increase for future clinical trials due to the availability of appropriate statistical methods and improved data management systems.

Intracranial myxopapillary ependymoma: case report

The authors report an unusual case of a myxopapillary ependymoma arising from the lateral ventricle. The patient, a 37-year-old woman, developed recurrent symptoms including scotomata, disorientation, and headache during two successive pregnancies before the definitive diagnosis. The causes of this ependymoma variant and its relationship to pregnancy are discussed.

Proliferative potential of brain tumors. Analyses with Ki-67 and anti-DNA polymerase alpha monoclonal antibodies, bromodeoxyuridine labeling, and nuclear organizer region counts

Histochemical analyses with Ki-67 and anti-DNA polymerase alpha monoclonal antibodies were done, and argyrophilic nucleolar organizer regions (Ag-NOR) were counted to estimate the proliferative potential of 200 brain tumors. The findings were compared with the bromodeoxyuridine labeling index (BrdU LI), or S-phase fraction. The proliferating cell indexes (PCI), determined by Ki-67 and anti-DNA polymerase alpha monoclonal antibodies were higher and Ag-NOR more numerous in medulloblastomas, glioblastomas, and metastatic carcinomas than in astrocytomas or meningiomas. The Ki-67 and DNA polymerase alpha PCI correlated with the BrdU LI (r = 0.87 and r = 0.84, respectively) and with each other (r = 0.94). The number of Ag-NOR correlated less strongly with these indexes in some tumors. These findings suggest that Ki-67 and anti-DNA polymerase alpha monoclonal antibodies may be useful for estimating the proliferative potential of individual tumors in routine clinical practice. The number of Ag-NOR, however, does not always reflect the growth potential of each tumor.

Immunohistochemical double staining with immunogold-silver and alkaline phosphatase to identify nuclear markers of cellular proliferation

To facilitate cell kinetics studies of brain tumors labeled with thymidine analogs, we developed a new method to identify nuclei labeled sequentially with bromodeoxyuridine (BUdR) and iododeoxyuridine (IUdR) by double staining with immunogold-silver and alkaline phosphatase. Patients received an intraoperative infusion of BUdR; excised tumor specimens were immediately labeled with IUdR in vitro, fixed with 70% alcohol, embedded in paraffin, and cut into 6 microns sections. The sections were incubated first with BR-3, a monoclonal antibody that recognizes only BUdR, and then with IU-4, a monoclonal antibody that recognizes both BUdR and IUdR; sections were counterstained with hematoxylin to identify unlabeled nuclei. Nuclei labeled only with IUdR stained red, whereas those labeled with BUdR or with both BUdR and IUdR stained black against a red background; unlabeled nuclei stained blue. This method was the most efficient differential staining technique to identify nuclei labeled only with IUdR and those labeled with BUdR among unlabeled nuclei.

Resection of dominant opercular gliosis in refractory partial epilepsy. Report of two cases

Frontal opercular gliosis in the dominant hemisphere caused medically refractory partial epilepsy in two patients. Both patients were aphasic during their seizures, but otherwise had normal speech. Magnetic resonance images showed well-demarcated lesions resembling tumors in each patient; on heavily T2-weighted images, the lesions were hyperintense compared with normal brain. Cortical mapping with subdural grids localized speech to the area of the lesions; therefore, the resections were performed under local anesthesia and speech was tested throughout the procedure. Postoperatively, both patients were seizure-free and had no new neurological deficits. Well-demarcated lesions, even in the dominant operculum, can be safely removed in patients with medically refractory partial epilepsy.

Preferential expression of the Drosophila rutabaga gene in mushroom bodies, neural centers for learning in insects

Seven lines were isolated with P element insertions in the cytogenetic vicinity of the learning and memory gene, rutabaga, from an enhancer detector screen designed to mark genes preferentially expressed in mushroom bodies. Six of these lines performed poorly in learning and memory tests, and several failed to complement an existing rutabaga allele. Molecular cloning revealed that the P elements were inserted in the putative promoter of the rutabaga gene. RNA in situ hybridization and immunohistochemistry demonstrated that the expression of the rutabaga gene, which encodes a Ca2+/calmodulin-responsive adenylyl cyclase, is markedly elevated in the mushroom bodies of normal flies and that the insertion elements compromised its expression in the new rutabaga mutants. The reisolation of a known learning and memory gene, but with a heretofore unknown expression pattern, strongly supports the postulate that mushroom bodies are principal sites mediating olfactory learning and memory.