Regulation of phosphatidylcholine homeostasis by calcium-independent phospholipase A2

Phosphatidylcholine (PtdCho) is the most abundant phospholipid in mammalian cell membranes and is essential for cell viability. The levels of this lipid must be tightly controlled to maintain homeostasis. Therefore, changes in the rate of PtdCho synthesis are generally balanced by changes in PtdCho catabolism and vice versa. It is commonly accepted that the rate of PtdCho synthesis is regulated by CTP:phosphocholine cytidylyltransferase (CT). However, it is not certain if PtdCho mass is regulated by specific catabolic enzyme(s). Our goal is to determine if PtdCho homeostasis is regulated by a phospholipase A₂ (PLA₂). To this end, we have prepared Chinese hamster ovary (CHO) cell lines that overexpress CT. CT activity is 7–10-fold higher in the transfected cells than in parental CHO cells. This increase in CT activity is associated with increases in both PtdCho synthesis and PtdCho catabolism. Glycerophosphocholine is the PtdCho catabolite that accumulates in the transfected cells, which suggests that PtdCho turnover is mediated by a phospholipase A₂ (PLA₂). Indeed, higher levels of calcium-independent PLA₂ activity are measured in the cytosols of the CHO cells that overexpress CT, compared to parental CHO cells. The elevated calcium-independent PLA₂ activity is associated with increases in the expression of the 80-kDa calcium-independent PLA₂ (iPLA₂). Together, these data suggest that the 80-kDa iPLA₂ may be modulated in response to changes in PtdCho levels and therefore is involved in the regulation of PtdCho homeostasis in CHO cells.     

delta 9-Tetrahydrocannabinol and cannabidiol: dose-dependent effects on evoked potentials in the hippocampal slice

The effects of (-) trans-delta 9-tetrahydrocannabinol (THC) and its metabolite cannabidiol (CBD) were investigated on evoked responses in the CA1 and dentate gyrus regions of the guinea pig transverse hippocampal slice. In both areas orthodromically evoked responses were enhanced by 10(-7) M THC, while 10(-6) M THC caused depression. Antidromic responses were not significantly affected. Antidromically-evoked inhibition in the CA1 region was decreased at low doses and unaffected at higher doses, while the facilitation by orthodromic interaction was unaffected at both dose ranges. The early part of the orthodromic field potential corresponding to the excitatory postsynaptic potential (EPSP) was enhanced at 10(-7) M in both areas. CBD (10(-6) M) decreased facilitation in CA1, and caused delayed excitation in the dentate granule layer. This study supports the conclusion that the biphasic effects of THC are dose dependent.     

Proffered papers 9.30–10.00 Monday 15 September 2003

Both the original Bethesda system and the current UK classifications of cervical cytology have proved robust but each has a major weakness in the area of abnormalities of uncertain significance. Cytologists recognize that sometimes it is simply impossible to differentiate between reactive and dyskaryotic material. For this reason, the Australian version of the Bethesda system introduced a new category of 'high grade inconclusive' with a recommendation for referral to colposcopy. Approximately 60% of such cases are found to have high grade lesions at colposcopy (Schoolland M, Sterrett G, Knowles S et al .). The present UK system even with the proposed changes requires of the pathologist, a decision as to whether such cases are probably high grade (=a report of moderate dyskaryosis) or not (= a report of borderline). This continues to ignore the fact that sometimes you just cannot tell, even on review. We have taken a consecutive series of 50 referral smears, reported as moderate dyskaryosis, where the histological outcome (by loop cone) is known. These cases were rescreened and then reviewed blind by a pathologist with extensive experience of the Australian NH & MRC modified Bethesda system. On review, the material was reclassified along NH & MRC lines. The results were compared with the biopsy findings in order to determine whether the category of 'inconclusive' might be of value in the context of the NHSCSP.     

Oral phenobarbital loading: a safe method of barbiturate and nonbarbiturate hypnosedative withdrawal.

We tested the efficacy and safety of oral phenobarbital loading, 120 mg/h until the end-point of mild intoxication is reached, for the treatment of hypnosedative withdrawal in 48 physically dependent patients, 14 of whom had a history of withdrawal seizures. None of the patients experienced seizures or any other symptoms of withdrawal during the study period, regardless of the phenobarbital half-life. The phenobarbital loading technique can be used in any hospital, not only those with access to specialized drug analysis laboratories. The method of treatment we describe allows the clinician to focus on issues such as rehabilitation instead of drug administration and manipulation of doses.     

Steroid metabolism by germ cells and spermatozoa in men after vasoepididymostomy.

The ability of germ cells (spermatocytes and spermatids) and spermatozoa present in human ejaculate to metabolize steroids was studied in men with obstructive infertility who had undergone vasoepididymostomy as corrective surgery. Steroid metabolism by spermatozoa in men who had undergone vasovasostomy was also investigated. Germ cells converted testosterone mainly to androstenedione. In addition to androstenedione, dihydrotestosterone and androstanediols were also formed in incubations using spermatids. Both types of germ cells converted estradiol to estrone. Spermatozoa from subjects who had undergone vasoepididymostomy or vasovasostomy converted testosterone to androstenedione as in normal men, while spermatozoa from infertile subjects converted testosterone mainly to dihydrotestosterone. Seminal fluid, free of germ cells, did not show steroid-metabolizing capability.     

Secretion and excretion of endogenously synthesized lipids by adult Haemonchus contortus in vitro

Results of the incorporation of carbon from 14C-glycerol into total, polar and nonpolar lipids in Haemonchus contortus (Nematoda: Trichostrongylidae) reveal that the radioactivity lost into the medium as lipids decreased during the first 3 h of incubation. This was followed by a drastic increase during the 4th h. Again, there was a decline by 75% during the 5th h. However, there was a slight increase in the nonpolar lipids during the 5th h.     

DNA diversity in the studies of genetic distance among isolated human populations in bosnia

Different degrees of isolation found in various part of Bosnia and Herzegovina may be induced by various factors. Bjelasnica-Treskavica region, located around 40 kilometers southwest from Sarajevo — capital of Bosnia and Herzegovina, is highly specific in that way. We chose three isolated communities: Dejcici, Bobovica and Lukomir for the study of genetic structure of isolated human populations. Based on general data three relative degrees of isolation/openness among the villages have been presumed as follows: first (lower-Dejcici), second (middle — Bobovica) and third (higher — Lukomir) 15 short tandem repeat (STR) loci and hypervariable region of mtDNA were chosen as a markers for study of population structure. Microsatellite allele frequencies, and mtDNA molecular diversity of Heterozigosity and coefficient of gene differentiation across all observed STR loci were estimated. Also, gene and nucleotide diversity of observed mtDNA regions were obtained. Genetic distance between three populations was calculated using method of Reynolds et al. (1983). For analysis of interpopulation relationship based on polymorphism of HV I and HV II region, estimation of pairwise differences was used. results of this research showed consistence with initial hypothesis on divergence based on socio-cultural factors.     

Diagnostic accuracy of cerebral angiography and computerized transaxial tomography.

Computer tomography (CT) of the brain has become widely accepted as an accurate method of studying a variety of intracranial diseases. In a prospective controlled study one group of radiologists interpreted cerebral angiograms and another interpreted CT studies undertaken in the same patients. The overall rates of diagnostic accuracy were similar (81 and 84% for angiography and CT, respectively), albeit less than reported in the literature, and thus support the contention that CT scanning should be available as the initial neuroradiologic examination whenever possible.