Gamma interferon synthesis by human thymocytes and T lymphocytes inhibited by cyclosporin A.

Cyclosporin A depresses the synthesis of gamma interferon by human thymocytes and T lymphocytes in vitro. This observation is of potential clinical significance because the long-term treatment of transplant patients with cyclosporin A, a widely used immunosuppressive agent, can give rise to B-cell lymphoma resulting from Epstein-Barr virus activation.

Vasectomy occlusion techniques for male sterilization.

BACKGROUND: Vasectomy is an increasingly popular and effective family planning method. A variety of vasectomy techniques are used worldwide, including various vas occlusion techniques (excision and ligation, thermal or electrocautery, and mechanical and chemical occlusion methods), as well as vasectomy with vas irrigation or with fascial interposition. Vasectomy guidelines largely rely on information from observational studies. Ideally, the choice of vasectomy techniques should be based on the best available evidence from randomized controlled trials. OBJECTIVES: The objective of this review was to compare the effectiveness, safety, acceptability and costs of vasectomy techniques for male sterilization. SEARCH STRATEGY: We searched the computerized databases of CENTRAL, MEDLINE, EMBASE, POPLINE and LILACS. In addition, we searched the reference lists of relevant articles and book chapters. SELECTION CRITERIA: We included randomized controlled trials comparing vasectomy techniques. DATA COLLECTION AND ANALYSIS: We assessed all titles and abstracts located in the literature searches. Two reviewers independently extracted data from articles identified for inclusion. Outcome measures include contraceptive efficacy, safety, discontinuation, and acceptability. MAIN RESULTS: Six studies met the inclusion criteria. One trial compared vas occlusion with clips versus a conventional vasectomy technique. No difference was found in failure to reach azoospermia. Three trials examined vasectomy with vas irrigation. Two studies looked at irrigation with water versus no irrigation, while one examined irrigation with water versus the spermicide euflavine. None found a difference between the groups for time to azoospermia. However, one trial reported that the median number of ejaculations to azoospermia was lower in the euflavine group compared to the water irrigation group. One high-quality trial compared vasectomy with fascial interposition versus vasectomy without fascial interposition. The fascial interposition group was less likely to have vasectomy failure. Fascial interposition had more surgical difficulties, but the groups were similar in side effects. Lastly, one trial found that an intra-vas was less likely to produce azoospermia than was no-scalpel vasectomy. More men were satisfied with the intra-vas device, however. AUTHORS' CONCLUSIONS: For vas occlusion with clips or vasectomy with vas irrigation, no conclusions can be made as those studies were of low quality and underpowered. Fascial interposition reduced vasectomy failure. An intra-vas device was less effective in reducing sperm count than was no-scalpel vasectomy. Randomized controlled trials examining other vasectomy techniques were not available. More and better quality research is needed to examine vasectomy techniques.

Scalpel versus no-scalpel incision for vasectomy.

BACKGROUND: Currently, the two most common surgical techniques for approaching the vas during vasectomy are the incisional method and the no-scalpel technique. Whereas the conventional incisional technique involves the use of a scalpel to make one or two incisions, the no-scalpel technique uses a sharp-pointed, forceps-like instrument to puncture the skin. The no-scalpel technique aims to reduce adverse events, especially bleeding, bruising, hematoma, infection and pain and to shorten the operating time. OBJECTIVES: The objective of this review was to compare the effectiveness, safety, and acceptability of the incisional versus no-scalpel approach to the vas. SEARCH STRATEGY: We searched the computerized databases of CENTRAL, MEDLINE, EMBASE, POPLINE and LILACS in May 2006. In addition, we searched the reference lists of relevant articles and book chapters. SELECTION CRITERIA: Randomized controlled trials and controlled clinical trials were included in this review. No language restrictions were placed on the reporting of the trials. DATA COLLECTION AND ANALYSIS: We assessed all titles and abstracts located in the literature searches and two authors independently extracted data from the articles identified for inclusion. Outcome measures included safety, acceptability, operating time, contraceptive efficacy, and discontinuation. MAIN RESULTS: Two randomized controlled trials evaluated the no-scalpel technique and differed in their findings. The larger trial demonstrated less perioperative bleeding (Odds ratio (OR) 0.49; 95% Confidence Interval (CI) 0.27 to 0.89) and pain during surgery (OR 0.75; 95% CI 0.61 to 0.93), scrotal pain (OR 0.63; 95% 0.50 to 0.80), and incisional infection (OR 0.21; 95% CI 0.06 to 0.78) during follow up than the standard incisional group. Both studies found less hematoma with the no-scalpel technique (OR 0.23; 95% CI 0.15 to 0.36). Operations using the no-scalpel approach were faster and had a quicker resumption of sexual activity. The smaller study did not find these differences; however, the study could have failed to detect differences due to a small sample size as well as a high loss to follow up. Neither trial found differences in vasectomy effectiveness between the two approaches to the vas. AUTHORS' CONCLUSIONS: The no-scalpel approach to the vas resulted in less bleeding, hematoma, infection, and pain as well as a shorter operation time than the traditional incision technique. No difference in effectiveness was found between the two approaches.

Scalpel versus no-scalpel incision for vasectomy.

BACKGROUND: Currently, the two most common surgical techniques for approaching the vas during vasectomy are the incisional method and the no-scalpel technique. Whereas the conventional incisional technique involves the use of a scalpel to make one or two incisions, the no-scalpel technique uses a sharp-pointed, forceps-like instrument to puncture the skin. The no-scalpel technique aims to reduce adverse events, especially bleeding, bruising, hematoma, infection and pain and to shorten the operating time. OBJECTIVES: The objective of this review was to compare the effectiveness, safety, and acceptability of the incisional versus no-scalpel vasectomy approach to the vas. SEARCH STRATEGY: We searched the computerized databases of CENTRAL, MEDLINE, EMBASE, POPLINE and LILACS in May 2006. In addition, we searched the reference lists of relevant articles and book chapters. SELECTION CRITERIA: Randomized controlled trials and controlled clinical trials were included in this review. No language restrictions were placed on the reporting of the trials. DATA COLLECTION AND ANALYSIS: We assessed all titles and abstracts located in the literature searches and two authors independently extracted data from the articles identified for inclusion. Outcome measures included safety, acceptability, operating time, contraceptive efficacy, and discontinuation. MAIN RESULTS: Two randomized controlled trials evaluated the no-scalpel technique and differed in their findings. The larger trial demonstrated less perioperative bleeding (Odds ratio (OR) 0.49; 95% Confidence Interval (CI) 0.27 to 0.89) and pain during surgery (OR 0.75; 95% CI 0.61 to 0.93), scrotal pain (OR 0.63; 95% 0.50 to 0.80), and incisional infection (OR 0.21; 95% CI 0.06 to 0.78) during follow up than the standard incisional group. Both studies found less hematoma with the no-scalpel technique (OR 0.23; 95% CI 0.15 to 0.36). Operations using the no-scalpel approach were faster and had a quicker resumption of sexual activity. The smaller study did not find these differences; however, the study could have failed to detect differences due to a small sample size as well as a high loss to follow up. Neither trial found differences in vasectomy effectiveness between the two approaches to the vas. AUTHORS' CONCLUSIONS: The no-scalpel approach to the vas resulted in less bleeding, hematoma, infection, and pain as well as a shorter operation time than the traditional incision technique. Although no difference in effectiveness was found between the two approaches, the sample sizes might have been too small to detect actual differences. Additional well-conducted randomized trials would help answer this question.

Childhood diarrhoea in a district in northeast Thailand: incidence and treatment choices.

Diarrhoeal disease is a major public health problem in Thailand. We collected information on childhood diarrhoea from a district in northeast Thailand, using various approaches which focus on both consumers and providers. The overall incidence of diarrhoea in the study area was 2.1 episodes per child per 12 months, with children under two years of age having a higher rate at 3.0 episodes per child per 12 months. Many episodes were not recognized as diarrhoeal episodes by caregivers, and treatment was sought in just over half of all episodes. Although children received an average of 2.4 items of medicine per episode, there was relatively low use of oral rehydration solutions. This study highlights the importance of assessing local beliefs when collecting data on diarrhoeal diseases in children, and the importance of continuing efforts to improve public health education on the management of diarrhoeal diseases.

Identification of a region in G protein gamma subunits conserved across species but hypervariable among subunit isoforms.

The heterotrimeric GTP binding proteins, G proteins, consist of three distinct subunits: alpha, beta, and gamma. There are 12 known mammalian gamma subunit genes whose products are the smallest and most variable of the G protein subunits. Sequencing of the bovine brain gamma(10) protein by electrospray mass spectrometry revealed that it differs from the human protein by an Ala to Val substitution near the N-terminus. Comparison of gamma isoform subunit sequences indicated that they vary substantially more at the N-terminus than at other parts of the protein. Thus, species variation of this region might reflect the lack of conservation of a functionally unimportant part of the protein. Analysis of 38 gamma subunit sequences from four different species shows that the N-terminus of a given gamma subunit isoform is as conserved between different species as any other part of the protein, including highly conserved regions. These data suggest that the N-terminus of gamma is a functionally important part of the protein exhibiting substantial isoform-specific variation.

Delayed first injection of the once-a-month injectable contraceptive containing 25 mg of medroxyprogesterone acetate and 5 mg of E(2)-cypionate: effects on ovarian function.

OBJECTIVE: To assess whether women who were administered the first injection of DMPA+E(2)C on day 7 of their menstrual cycle (delayed injection) exhibit the same degree of ovarian suppression as women who receive it on day 5 of their menstrual cycle. DESIGN: Multicenter, randomized controlled trial. SETTING: Reproductive health clinics. PATIENT(S): Women aged between 18 and 38 years (inclusive) willing to use DMPA+E(2)C as their method of contraception. INTERVENTION(S): Participants received a DMPA+E(2)C injection on day 5 (control group, n = 41) or day 7 (delayed-injection group, n = 117) of their menstrual cycle. MAIN OUTCOME MEASURE(S): Ovarian activity and follicular development determined by serial serum progesterone levels and vaginal ultrasound. RESULT(S): Participants who received DMPA+E(2)C on day 5 of their menstrual cycle (control group) exhibited no more than limited follicular growth (no follicle >16 mm). Of those women who received DMPA+E(2)C on day 7 of their menstrual cycle (delayed-injection group), 21 (18%) showed some follicular growth, of whom 4 (3%) ovulated. CONCLUSION(S): The first injection of DMPA+E(2)C given on day 7 of a menstrual cycle does not provide the same inhibition of ovarian activity as that observed when it is administered on day 5 of the menstrual cycle.

Delayed first injection of the once-a-month injectable contraceptive containing 25 mg medroxyprogesterone acetate and 5 mg estradiol-cypionate: effects on cervical mucus.

The objectives of this study were to assess whether women who were administered the first injection of the once-a-month contraceptive containing estradiol cypionate and 25 mg depot-medroxyprogesterone acetate (MPA+E(2)C) on Day 7 of their menstrual cycle (delayed injection) exhibit the same degree of cervical mucus changes as women who receive it on Day 5 of their menstrual cycle. This was a multicenter, randomized, controlled clinical trial. A total of 158 women, aged between 18 and 38 years (inclusive), who, were willing to use MPA+E(2)C as their contraceptive method participated in the trial. Participants received a MPA+E(2)C injection on Day 5 (control group, n = 41) or Day 7 (delayed-injection group, n = 117) of their menstrual cycle. Participants who received MPA+E(2)C on Day 5 of their menstrual cycle (control group) exhibited fair or poor mucus quality and poor sperm penetration. Of those women who received MPA+E(2)C on Day 7 of their menstrual cycle (delayed-injection group), 3 (3%) showed good mucus or good sperm penetration at some time point during follow-up. It is possible to conclude that the first injection of MPA+E(2)C given on Day 7 of a menstrual cycle does not provide the same degree of inhibition of mucus quality and sperm penetration as that observed if it is administered on Day 5. However, the theoretical risk of pregnancy after receiving MPA+E(2)C on Day 7 would be expected to be low.

Biochemical markers of cerebral injury in patients with minor head trauma and ethanol intoxication.

OBJECTIVE: To determine whether biochemical markers can selectively identify those intoxicated patients with presumed minor head injuries who are likely to have CT evidence of intracranial injury. METHODS: Patients presenting to the ED with simultaneous presumed minor head trauma and ethanol intoxication were prospectively entered into this cross-sectional study. Following phlebotomy, all patients received cranial CT. Associations between the presence of an abnormal CT scan for injury and serum levels of the following biochemical markers were sought: serum catecholamines, creatine kinase-brain band (CK-BB), and serum amylase. Serum levels are reported as mean +/- SEM. RESULTS: Nine of the 107 patients (8.4%; 95% CI 3.9-15.4%) had evidence of intracranial injury on CT. Mean serum CK-BB (16.1 +/- 3.7 vs 13.2 +/- 9.6 ng/mL), serum norepinephrine (913 +/- 117 vs 1,089 +/- 76 pg/mL), and serum amylase (64.9 +/- 14.8 vs 84 +/- 4.7 U/L) levels were not significantly different in patients with and without CT evidence of intracranial injury, respectively. Mean serum epinephrine (298 +/- 54 vs 167 +/- 18 pg/mL; p = 0.03) and serum dopamine (218 +/- 50 vs 130 +/- 9 pg/mL; p = 0.014) levels were significantly elevated in the group with intracranial injury on CT. A threshold level of serum dopamine > or = 140 pg/mL yields a sensitivity of 89% (95% CI 52-100%) and a specificity of 80% (95% CI 70-87%) for CT-evident injury. A threshold level of serum epinephrine > or = 218 pg/mL yields a sensitivity of 89% (95% CI 52-100%) and a specificity of 80% (95% CI 70-87%) for CT-evident injury. CONCLUSION: Elevated serum epinephrine and dopamine levels are associated with intracranial CT-evident injury for ethanol-intoxicated patients with presumed minor head injuries. The potential use of these biochemical markers to guide a more selective approach to cranial CT scanning warrants further evaluation.

Effects of anticholinergic-antiparkinsonian drugs on striatal neurotransmitter levels of rats intoxicated with soman.

Antimuscarinic drugs possessing antiparkinson activity that were effective in preventing convulsions induced by the organophosphorus cholinesterase (ChE) inhibitor soman were studied for their effects on spinal cord ChE activity and striatal levels of acetylcholine (ACh) and catecholamines in soman-intoxicated rats. Either biperiden (BPR) or trihexyphenidyl (THP) was administered to rats at an anticonvulsant dose (0.125 mg/kg, IM) in the presence or absence of soman (100 micrograms/kg, SC). The time course (up to 2 h) for ChE activity and levels of ACh and catecholamines were measured after soman, BPR, THP, soman and BPR, or soman and THP treatment. Soman rapidly inhibited ChE activity (65-75%; 15-120 min) and increased ACh levels (35%; at 30 min). It did not affect norepinephrine or dopamine (DA), but elevated at later time points (60-120 min) levels of the DA metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), thus indicating increased DA turnover. BPR and THP alone reduced striatal ACh level from control, but did not affect any other neurochemical parameters studied. THP and BPR each reversed the effects of soman on DOPAC and HVA levels, but neither affected ChE activity nor ACh level induced by soman. Thus, our findings suggest that the anticonvulsant effects of BPR and THP in soman poisoning may be attributed to their earlier reported muscarinic receptor blocking properties.

Terbutaline pump maintenance therapy after threatened preterm labor for preventing preterm birth.

BACKGROUND: Women with preterm labor that is arrested with tocolytic therapy are at increased risk of recurrent preterm labor. Terbutaline pump maintenance therapy has been given to such women to decrease the risk of recurrent preterm labor, preterm birth, and its consequences. OBJECTIVES: To determine the effectiveness and safety of terbutaline pump maintenance therapy after threatened preterm labor in preventing preterm birth and its complications. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register (searched May 2002) and the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2002). SELECTION CRITERIA: Randomized trials comparing terbutaline pump maintenance therapy with alternative therapy, placebo, or no therapy after threatened preterm labor. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed the studies for inclusion and then extracted data from eligible studies. MAIN RESULTS: We included two studies. Terbutaline pump maintenance therapy did not appear to offer any advantages over the saline placebo pump or oral terbutaline maintenance therapy in preventing preterm births by prolonging pregnancy or its complications among women with arrested preterm labor. The weighted mean difference (WMD) for gestational age at birth was -0.1 weeks (95% confidence interval (CI) -1.7 to 1.4) for terbutaline pump therapy compared with saline placebo pump for both trials combined and 1.4 weeks (95% CI -1.1 to 3.9) for terbutaline pump versus oral terbutaline therapy for the first trial. The second trial reported a relative risk (RR) of 1.17 (95% CI 0.79 to 1.73) of preterm birth (less than 37 completed weeks) and a RR of 0.97 (95% CI 0.51 to 1.84) of very preterm birth (less than 34 completed weeks) for terbutaline pump compared with saline placebo pump. Terbutaline pump therapy also did not result in a higher rate of therapy continuation or a lower rate of infant complications. No data were reported on long-term infant outcomes, costs, or maternal assessment of therapy. REVIEWER'S CONCLUSIONS: Terbutaline pump maintenance therapy has not been shown to decrease the risk of preterm birth by prolonging pregnancy. Furthermore, the lack of information on the safety of the therapy, as well as its substantial expense, argues against its role in the management of arrested preterm labor. Future use should only be in the context of well-conducted, adequately powered randomized controlled trials.

Vasectomy occlusion techniques for male sterilization.

BACKGROUND: Vasectomy is an increasingly popular and effective family planning method. A variety of vasectomy techniques are used worldwide including various vas occlusion techniques (excision and ligation, thermal or electrocautery, and mechanical and chemical occlusion methods), vas irrigation and fascial interposition. Vasectomy guidelines largely rely on information from observational studies. Ideally, the choice of vasectomy techniques should be based on the best available evidence from randomized controlled trials. OBJECTIVES: The objective of this review was to compare the effectiveness, safety, acceptability and costs of vasectomy techniques for male sterilization. SEARCH STRATEGY: We searched the computerized databases the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Popline and LILACS. In addition, we searched the reference lists of relevant articles and book chapters. SELECTION CRITERIA: We included randomized controlled trials and controlled clinical trials comparing vasectomy techniques. DATA COLLECTION AND ANALYSIS: We assessed all titles and abstracts located in the literature searches and two reviewers independently extracted articles identified for inclusion. Data were presented in the text of the review. Outcome measures include contraceptive efficacy, safety, discontinuation, and acceptability. MAIN RESULTS: Two trials compared vas occlusion with clips versus a conventional vasectomy technique; both were of poor quality. Neither trial found a difference between the two groups with regard to the primary outcome of failure to reach azoospermia. Four trials examined vas irrigation: three compared water irrigation with no irrigation and one compared water irrigation with euflavine. All of the trials were of poor quality. None of the trials found a significant difference between the groups with respect to the primary outcome of time to azoospermia. However, one trial found that the median number of ejaculations to azoospermia was significantly lower in the euflavine group compared to the water irrigation group. The one trial that compared vasectomy with fascial interposition versus vasectomy without fascial interposition was a high quality, large study that has only been partially reported at the time of this review. The fascial interposition group was significantly more likely to be related to vasectomy success (azoospermia) at 22 weeks. However, fascial interposition also was associated with significantly more surgical difficulties. REVIEWERS' CONCLUSIONS: No conclusions can be made about the effectiveness, safety, acceptability and costs of vas occlusion technique or vas irrigation as studies that examined these were of low quality and underpowered. Fascial interposition is associated with improved vasectomy success but is associated with some increased surgical difficulty. Randomized controlled trials examining other vasectomy techniques were not available. More research is required to examine vasectomy techniques.

Decision making for the critically ill neonate near the end of life.

Our purpose was to review the medical records of 122 infants who died in our neonatal intensive care unit (NICU) to characterize decision making for the critically ill neonate near the end of life. The majority of deaths (72%) were related to some complication of prematurity. Families participated in the decision-making process in 75% of the instances. A decision was made to limit, withdraw, or withhold life-sustaining treatment for 82% of the infants. At the time of decision making, prognosis was judged to be poor or hopeless and the burdens of treatment unacceptable for 90% of the infants. This study confirms that health care providers and families together can confront the ethical decision of whether to continue or forego life-sustaining treatment for the critically ill neonate near the end of life and, in the majority of cases, will choose to limit, withdraw, or withhold such support.

Whole blood ionized magnesium in the healthy neonate.

OBJECTIVE: We aimed to determine the normal range of ionized magnesium (IMg2+) concentration at birth and 24 hours of life in the healthy, term (37 to 41 weeks old) neonate. METHODS: Cord blood was obtained from the umbilical vein of 30 patients. In addition, blood was obtained from 32 infants at 24 hours of life. Whole blood was analyzed to determine IMg2+ concentration, ionized calcium concentration, and pH. RESULTS: The normal range of IMg2+ concentration (mean +/- 2 SD) was found to be 0.40 to 0.56 mmol/L (0.97 to 1.36 mg/dL) at both birth and 24 hours of life. CONCLUSIONS: The normal range of IMg2+ concentration (mean +/- 2 SD) in the healthy neonate at birth and 24 hours of life is 0.40 to 0.56 mmol/L (0.97 to 1.36 mg/dL). This range can serve as a reference value for future studies regarding the clinical usefulness of IMg2+ concentration determination in neonatal disease states.

Regulation of interleukin-2 synthesis in human thymocytes.

This study was designed to investigate whether or not human thymocytes can synthesize and respond to interleukin-2 (IL-2). Thymocytes were isolated from thymic sections obtained during cardiac surgery, and immature, heavy (density, 1.070-1.075 g/ml) thymocytes were separated from mature, light (density, less than or equal to 1.065 g/ml) thymocytes by buoyant density centrifugation. Thymocytes were stimulated with concanavalin A (con A), B lymphoblastoid (Bl) cells, phorbol myristate acetate (PMA), or with a combination of two or more inducing agents. Culture supernatants were analyzed for IL-2 activity by measuring the proliferation of an IL-2-dependent cytotoxic T cell line ( CTLL -A11). The response of human thymocytes to endogenous or exogenous (purified) IL-2 was assessed by determining their proliferative activity and their capacity to consume and absorb IL-2. Stimulation with con A in combination with PMA or Bl cells resulted in secretion of IL-2 by dense, immature thymocytes, low-density, mature thymocytes, and unfractionated thymocytes, and in an increase in [3H]thymidine incorporation. IL-2 synthesis preceded the proliferative response and required the continuous presence of con A. It was inhibited by cyclosporin A (CsA), an immunosuppressant which inhibits T cell activation and proliferation. As a result of the inhibition of endogenous IL-2 synthesis, thymocyte proliferation at 120 h of culture was also inhibited. CsA did not inhibit proliferation at 48 h of culture when exogenous IL-2 absorption became evident, but before the onset of the IL-2-dependent proliferative response.

Vasectomy techniques for male sterilization: systematic Cochrane review of randomized controlled trials and controlled clinical trials.

BACKGROUND: The review aimed to compare the effectiveness, safety and acceptability of vasectomy techniques for male sterilization. METHODS: We searched five computerized databases and reference lists of relevant articles and book chapters for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) comparing vasectomy techniques. Two reviewers independently extracted data from eligible articles. RESULTS: Two poor-quality trials compared vas occlusion with clips versus a conventional technique, and four poor-quality trials examined vas irrigation with water versus no irrigation or irrigation with euflavine. No significant differences regarding the primary outcome of time to azoospermia were found. However, one trial reported fewer median number of ejaculations to azoospermia with euflavine rather than water irrigation. An interim report of a high-quality trial comparing vasectomy with and without fascial interposition found more azoospermia with fascial interposition but also more surgical difficulties. CONCLUSIONS: No conclusions can be reached regarding the effectiveness, safety and acceptability of vas occlusion techniques or vas irrigation since only low-quality, underpowered studies were available. Fascial interposition had improved vasectomy success but also increased surgical difficulty. High-quality, adequately reported RCTs are required. More work is also needed in the standardization of follow-up protocols, evaluation of vasectomy success and failure, recanalization and analytical methods.

Heterogeneous processing of a G protein gamma subunit at a site critical for protein and membrane interactions.

The G protein gamma5 subunit is selectively associated with specific G protein alpha subunits [Wilcox, M. D., et al. (1995) J. Biol. Chem. 270, 4189] and is localized preferentially in focal adhesion plaques [Hansen, C. A., et al. (1996) J. Cell Biol. 126, 811]. What determines the differential association of G proteins and their subunits with specific cellular structures or compartments is not clear, but one factor could be variation in the pattern of processing of the proteins. To study gamma5 subunit diversity and modifications, G protein subunits were fractionated on an HPLC phenyl column and analyzed with a gamma5-specific antiserum. The gamma5 eluted from the column as two peaks of immunoreactivity. Analysis by matrix-assisted laser desorption ionization (MALDI) mass spectrometry and electrospray ionization tandem mass spectrometry revealed that the first immunoreactive peak corresponded to the predicted gamma5 isoform (N-terminally acetylated after removal of methionine, C-terminally geranylgeranylated and carboxymethylated with removal of the last three amino acids), while the second peak of immunoreactivity contained a gamma5 isoform isoprenylated at the C-terminus but retaining its three terminal amino acids. This alternatively processed protein is the predominant gamma5 subunit isoform associated with Go and Gi proteins purified from bovine brain. These results describe a new C-terminal processing pattern for G protein gamma subunits and establish the principle that G protein gamma subunits can be heterogeneously modified at their C-termini. This is a site on the gamma subunit critical for membrane and protein-protein interactions of G proteins. These results open the possibility that one determinant of the localization of G proteins in cells could be the pattern of processing of their gamma subunit constituents.

Gamma interferon induction in human thymocytes activated by lectins and B cell lines.

Human thymocytes in culture synthesized small quantities of interferon (IFN) when stimulated by the lectins concanavalin A or phytohemagglutinin. IFN production by lectin-activated thymocytes was enhanced in the presence of live B lymphoblastoid cells, irradiated B lymphoblastoid cells, or the conditioned medium from B lymphoblastoid cell cultures. The IFN synthesized in mixed cultures had characteristics of IFN-gamma, whereas the IFN synthesized by B lymphoblastoid cells alone could be identified as IFN-alpha on the basis of its neutralization with specific antisera and stability at pH 2. These findings indicate that human thymocytes in culture synthesize IFN-gamma and that B lymphoblastoid cells and their products considerably stimulate IFN-gamma synthesis by lectin-activated human thymocytes in culture. This stimulation was not diminished in the presence of antibodies to IFN-alpha, indicating that IFN-alpha production by B lymphoblastoid cells was not responsible for the stimulatory effect. Removal of adherent cells from thymocyte suspensions did not abrogate IFN-gamma production.