Molecular basis of defective anion transport in L cells expressing recombinant forms of CFTR

Cystic fibrosis (CF) is caused by mutations in the gene encodinga chloride channel called the CF transmembrane conductance regulator(CFTR). A single mutation in this gene, deletion of three nucleotidesthat leads to the absence of phenylalanine 508 (i.e., F508),is found on 70% of all CF chromosomes. To explore the molecularmechanism(s) responsible for defective chloride transport inpatients with CF, we have studied the processing, localization,and function of wild type (W.T.), F508 and G551D CFTR (a GDmissense mutation at position 551) in retrovirus transducedL cells. Cell transduced with W.T. CFTR expressed a 170 kd CFTRprotein that was endoglycosidase H (Endo H) resistant, localizedto the plasma membrane, and generated a cAMP-mediated anionconductance (G_Cl) when stimulated with standard concentrationsof forskolin (5 µM), cpt cAMP (400 µM) and IBMX(100 µM). The G551D CFTR was indistinguishable from W.T.CFTR with respect to post-translational processing and localization,but it did not produce a cAMP-activated G_CI in response to thestandard stimulation cocktail. However, raising the IBMX concentrationto 4 mM produced Gc, in G551D expressing cells. Cells transducedwith F508 CFTR expressed an Endo H sensitive CFTR protein (140kd) that was found in a cytosolic, perinuclear location. Thesecells did not respond to the standard cocktail, but 20% of cellsincreased G_CI when the cocktail contained 4 mM IBMX. Incubationof cells at 26°C for 48 hours prior to analysis elicitedresponses in F508 expressing cells at low IBMX concentrations,but had no effect on the responses of cells expressing W.T.or G551D CFTR. The response of F508 to 26°C was associatedwith plasma membrane localization of CFTR protein. These resultssuggest that there are two mechanisms whereby CFTR mutationslead to loss of cAMP-responsive GCI. First, shown by G551D CFTR,the protein can be processed and targeted to the plasma membranecorrectly, but lack full responsiveness to stimulation by cAMP.Second, as examplified by F508 CFTR, a partially functionalprotein which is not targeted to its correct cellular locationcan also lead to loss of the cAMP, responsive G_CI.     

Missense mutations in the beta-myosin heavy-chain gene cause central core disease in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is an important cause of sudden death in apparently healthy young individuals. In less than half of kindreds with HCM, the disease is linked to the beta-myosin heavy-chain gene locus (MYH7). We have recently described two missense MYH7 gene mutations [Arg-403 to Gln (R403Q) and Leu-908 to Val (L908V)] and found that the mutant message is present in skeletal muscle soleus) and that the mutant beta-myosin obtained from soleus muscle has abnormal in vitro motility activity. Having identified a second kindred with the R403Q mutation, and 3 other kindreds with two additional mutations (G741R and G256E), we performed histochemical analysis of soleus muscle biopsies from 25 HCM patients with one of these four mutations. Light microscopic examination of the NADH-stained biopsies revealed the presence of central core disease (CCD) of skeletal muscle, a rare autosomal dominant nonprogressive myopathy characterized by a predominance of type I "slow" fibers and an absence of mitochondria in the center of many type I fibers. CCD was present in 10 of 13 patients with the L908V mutation, 5 of 8 patients with the R403Q mutation, 1 of 3 patients with the G741R mutation, and 1 patient with the G256E mutation. Mild-to-moderate myopathic changes with muscle fiber hypertrophy were present in 16 patients. Notably, CCD was present in 2 adults and 3 children with the L908V mutation who did not have cardiac hypertrophy. In contrast, soleus muscle samples from 5 patients from 4 kindreds in which HCM was not linked to the MYH7 locus showed no myopathy or CCD. Soleus muscle biopsies from 5 control subjects also showed normal histology. This work demonstrates that (i) MYH7-associated HCM is often a disease of striated muscle but with predominant cardiac involvement and (ii) a subset of HCM patients with MYH7 gene missense mutations have CCD.     

Differential effects of MK-801, NMDA and scopolamine on rats learning a four-member repeated acquisition paradigm

The glutamatergic (NMDA) and cholinergic neurotransmitter systems have been extensively implicated as neurochemical mediators of learning processes. These two systems may differentially affect learning; for example, although both the cholinergic antagonist scopolamine and the NMDA antagonist MK-801 reduced overall accuracy of rats in a 3-member repeated acquisition paradigm, the nature of the underlying error patterns produced by the two drugs differed significantly: rats administered scopolamine produced a pattern of skipping errors, while administration of MK-801 predominantly increased perseverative errors (Cohn et al., 1992). The present experiment extended that study to examine whether a more complex task, i.e. a 4-member repeated acquisition paradigm, would alter the nature of the error patterns resulting from administration of each drug, and whether NMDA itself would increase accuracy on the repeated acquisition paradigm. MK-801 (0.05-0.3mg/kg i.p.) significantly decreased overall accuracy in a dose-dependent manner, and the rats produced a pattern of errors similar, although not identical to, that noted in the 3-member paradigm, including perseverative errors early in the sequence, but additional skipping errors at later points in the sequence. MK-801 dramatically decreased correct initiation of a sequence following an error at any point in the sequence. NMDA (10.0-30.0mg/kg) itself did not facilitate sequence acquisition, i.e. it did not affect overall accuracy. However, it was the only drug to increase the frequency of correctly reinitiating a sequence following an incorrect first or an incorrect second sequence member. Like MK-801, scopolamine (0.5-3.0mg/kg i.p.) also produced a decline in overall accuracy which was again achieved primarily through increased skipping errors. Scopolamine did not, however, interfere with correctly reinitiating a sequence either after successful completion of a sequence, or after an error. These findings suggest that cholinergic and glutamatergic compounds exert their effects on learning through different behavioral mechanisms.     

Men''s disclosure of HIV test results to male primary sex partners.

We evaluated disclosure of human immunodeficiency virus (HIV) antibody status to a main sex partner and the impact on the relationship in men who have sex with men and who are enrolled in the Acquired Immunodeficiency Syndrome (AIDS) Community Demonstration Projects cohorts. Eighty-nine percent of both seronegative and seropositive men disclosed the results to their main sex partner. Seventy percent of the seronegative men and 82% of the seropositive men who did so reported that the relationship remained "as strong as ever" after 6 months. Most men who did not disclose their test results to their main partner reported being "single" after 6 months.     

Atrioventricular valve replacement with a Hancock porcine xenograft

The Hancock porcine xenograft valve was the first commercially prepared, quality-controlled tissue valve. The National Institutes of Health group began implantation of this valve in 1970 and reported on the first 5 years of their results, which was one of the longest follow-ups of that valve at that particular time. Since then there have been a number of centers that have had long-term experience with thousands of these valves. In retrospect, it is now clear that some of the conclusions made by the National Institutes of Health group have not come to pass, such as this valve being the "valve of choice" for all patients. "Valve of choice" is a relative term and may be one valve for one patient and another valve for another patient. This report was important in bringing together some of the first medium-term data and pointing out that, even in this valve, there was some small degree of thromboembolism. The paper also provided a historical look at the methods of data analysis that were in use in the early 1970s compared with those now used in 1991. Actuarial curves were not yet commonly used, nor were percent/patient-year linearized results. Valve types were mixed as well. Hemodynamic data, always a strong point of National Institutes of Health data analysis, were excellent. The use of this valve became a fairly standard device and has been retrospectively analyzed by a number of centers, suggesting that now it is better used in the older patient or in patients who cannot take warfarin sodium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Longitudinal neurological follow-up of a group of HIV-seropositive and HIV-seronegative hemophiliacs: results from the hemophilia growth and development study

BACKGROUND: Boys and young men with hemophilia treated with factor infusions before 1985 had a substantial risk of acquiring the human immunodeficiency virus (HIV) and the acquired immunodeficiency syndrome. This study was designed to assess the effects of HIV and hemophilia per se on neurological function in a large cohort of subjects with hemophilia, and to investigate the relationships between neurological disease and death during follow-up. METHODS: Three hundred thirty-three boys and young men (207 HIV seropositive and 126 HIV seronegative) were evaluated longitudinally in a multicenter, multidisciplinary study. Neurological history and examination were conducted at baseline and annually for 4 years. The relationship between neurological variables, HIV serostatus, CD4+ cell counts, and vital status at the conclusion of the study was examined using logistic regression models. RESULTS: The risks of nonhemophilia-associated muscle atrophy, behavior change, and gait disturbance increased with time in immune compromised HIV-seropositive subjects compared with HIV seronegative or immunologically stable HIV-seropositive subjects. The risk of behavior change in immune compromised HIV-seropositive hemophiliacs, for example, rose to 60% by year 4 versus 10% to 17% for the other study groups. Forty-five subjects (13.5%), all of whom were HIV seropositive, died by year 4. Subjects who died had had increased risks of hyperreflexia, nonhemophilia-associated muscle atrophy, and behavior change. CONCLUSIONS: These results indicate that immune compromised, HIV-seropositive hemophiliacs have high rates of neurological abnormalities over time and that neurological abnormalities were common among subjects who later died. By contrast, immunologically stable HIV-seropositive subjects did not differ from the HIV-seronegative participants. Hemophilia per se was associated with progressive abnormalities of gait, coordination, and motor function.     

Extradural dermoid tumours of the posterior fossa

Dermoid tumours in children usually occur in two locations: at the anterior fontanelle and on the occipital squama. An exceptional site of origin for a posterior fossa dermoid cyst is the extradural space. There are only six previous cases of this situation reported in the literature. A series of 103 subscalp and calvarial masses in children were reviewed and three children are reported with extradural dermoids of the posterior fossa, which communicated with the skin through midline occipital dermal sinuses. All three children were seen after the rapid growth or the formation of an abscess in a previously noted occipital subcutaneous mass present since birth. Although computed tomography or magnetic resonance imaging showed the dermal sinus and the intracranial tumour, these studies were unable to ascertain the intradural or extradural nature of the tumours, their exact origin only being established at operation. Histopathological study showed preclinical signs of infection in the two patients that had not yet formed an abscess. It is suggested that early neurosurgical treatment of these neoplasms should be done to prevent the development of severe intracranial infection. The previously reported simplicity of surgical removal of occipital extradural dermoids was not confirmed in this series.     

Adenocarcinoma of the uterine cervix metastatic to lymph nodes

OBJECTIVE: We set out to evaluate the prognostic factors in cervical adenocarcinoma metastatic to lymph nodes. STUDY DESIGN: We performed a retrospective review of 40 patients with cervical adenocarcinoma and lymph node metastasis from 1976 to 1996. RESULTS: Thirty-four patients had adenocarcinoma, and six had adenosquamous carcinoma. Median survival was 50 months. The median survival for patients with stage I disease was 69 months. Stage at diagnosis, treatment with radical hysterectomy, and receiving adjuvant therapy were associated with prolonged survival. A trend toward improved survival was noted with the use of concurrent radiation and chemotherapy as an adjuvant therapy. CONCLUSIONS: Adenocarcinoma metastatic to the lymph nodes does not have a uniformly poor prognosis, especially with early-stage disease. Improved survival was observed with the use of adjuvant therapy, specifically the use of combined chemotherapy and radiation after radical hysterectomy. The optimal therapy in this setting is yet to be determined. (Am J Obstet Gynecol 1998;178:1131-7.)