Pharmacological re-evaluation of a GABA(B) receptor antagonist CGP 47332A in rat brain

In rat neocortical slices maintained in Mg(2+)-free Krebs medium, the gamma-aminobutyric acid (GABA(B)) receptor agonist baclofen concentration-dependently depressed the frequency of spontaneous discharges (EC(50)=12 microM). This was reversibly antagonised by (R, S)-3-amino-2-hydroxy-propyl-P-n-butyl-phosphinic acid (CGP 47332A) (25, 100, 300 microM) which produced rightwards shifts of the baclofen concentration-response curves (pA(2) value=4.8+/-0.1). In electrically stimulated slices preloaded with [3H]GABA, CGP 47332A increased its release (EC(150)=100 microM) through antagonism of GABA(B) autoreceptors. Although CGP 47332A was some six times weaker on GABA(B) auto- than on heteroreceptors, yet its congener lacking the beta-hydroxy substituent displays equal potency in both binding (IC(50)=38 microM) and GABA(B) autoreceptor functional studies (EC(150)=38 microM) as previously reported [Froestl, W., Mickel, S.J. , Von Sprecher, G., Diel, P.J., Hall, R.G., Maier, L., Strub, D., Melillo, V., Baumann, P.A., Bernasconi, R., Gentsch, C., Hauser, K., Jaekel, J., Karlsson, G., Klebs, K., Maitre, L., Marescaux, C., Pozza, M.F., Schmutz, M., Steinmann, M.W., Van Riezen, H., Vassout, A., Mondadori, C., Olpe, H.R., Waldmeier, P.C., Bittiger, H., Phosphinic acid analogues of GABA: 2. Selective, orally active GABA(B) antagonists. J. Med. Chem. 38 (1995) 3313-3331.].

Comparative potencies of CGP 47654A and CGP 46165A as GABA(B) receptor antagonists in rat brain

In rat neocortical slices maintained in Mg2+-free Krebs medium, the gamma-aminobutyric acid (GABAB) receptor agonist baclofen concentration-dependently depressed the frequency of spontaneous discharges (EC50 = 6.1 microM). This was reversibly antagonised by 3-aminopropyl-(1,1-difluoro-n-butyl)-phosphinic acid (25, 100, 500 microM) (CGP 47654A) and 3-aminopropyl-P-(alpha-hydroxybenzyl)-phosphinic acid (CGP 46165A) (50, 100, 400 microM) which produced rightwards shifts of the baclofen concentration-response curves, with respective pA2 values of 4.9+/-0.2 and 4.6+/-0.15. Although relatively potent on GABAB heteroreceptors studied here, CGP 47654A and CGP 46165A were 5 and 50 times weaker, respectively, as GABAB autoreceptor antagonists [Froestl, W., Mickel, S.J., Von Sprecher, G., Diel, P.J., Hall, R.G., Maier, L., Strub, D., Melillo, V., Baumann, P.A., Bernasconi, R., Gentsch, C., Hauser, K., Jaekel, J., Karlsson, G., Klebs, K., Maitre, L., Marescaux, C., Pozza, M.F., Schmutz, M., Steinmann, M.W., Van Riezen, H., Vassout, A., Mondadori, C., Olpe, H.R., Waldmeier, P.C., Bittiger, H., 1995. Phosphinic acid analogues of GABA. 2. Selective, orally active GABAB antagonists. J. Med. Chem. 38: 3313-3331.], representing potentially useful ligands for differentiating GABA hetero- and autoreceptors.

Sixty percent salvage rate for germ-cell tumours using sequential m-BOP, surgery and ifosfamide-based chemotherapy

BACKGROUND

In germ-cell tumours (GCT), there is continuing controversy over the relative merits of dose dense therapy (increased frequency over a given time) versus vertical intensification (increased dose per fraction). The value of using a cisplatin-based dose dense approach in the salvage setting has not been documented and in addition the role of methotrexate remains uncertain. This paper reviews results from our investigations of these issues.

PATIENTS AND METHODS

Between 1987 and 1996, 65 patients with relapsing or refractory germ-cell tumour received weekly m-BOP (methotrexate, bleomycin, vincristine and cisplatin) as salvage therapy. Residual masses were excised if possible and patients progressing after this received cisplatin and ifosfamide based chemotheraphy with or without high dose chemotherapy (HDCT) consolidation.

RESULTS

With a median follow-up of 33 months, 34% are progression free following m-BOP, 11% who had surgery for residual masses which showed viable cancers are progression free. A further 15% who progressed following m-BOP with or without surgery were rendered progression free by third-line therapy.

CONCLUSIONS

The use of m-BOP as second line therapy with deferment of cisplatin and ifosfamide based treatment to third line therapy with consolidation of third line responses with HDCT, leads to an overall progression-free survival of 60%. It does not appear that M-BOP prejudiced the response to third line therapy suggesting a lack of cross resistance. The potentially lower risk of leukaemia and infertility from m-BOP requires further evaluation.

The management of residual masses after chemotherapy in metastatic seminoma

OBJECTIVE

To review our experience in management of residual masses after chemotherapy for metastatic seminoma.

PATIENTS AND METHODS

The study comprised a review of 107 patients with metastatic seminoma, treated with initial chemotherapy from 1978 to 1996. Forty-three patients had residual masses detected by computed tomography after chemotherapy, while 64 achieved a complete response. Residual masses were classified radiologically as <3 cm or >/=3 cm and as well- or poorly defined. Of the patients with residual masses, 19 underwent surgery, while 24 were observed.

RESULTS

Viable cancer was present in six of 11 patients with well-defined residual masses of >/=3 cm (positive histology in three of six undergoing surgery and site relapses in three of five observed), one of 14 patients with poorly defined masses of >/=3 cm (negative histology in nine undergoing surgery and site relapse in one of five observed), and in none of 17 patients with residual masses of <3 cm (negative histology in four undergoing surgery and no site relapses in 13 observed; one additional patient in this group died from treatment complications).

CONCLUSION

Patients with a complete response after chemotherapy, a residual mass of <3 cm and a poorly defined residual mass of >/=3 cm can be observed, reserving intervention for recurrent or progressive disease. Well-defined residual masses of >/=3 cm should be resected because there is a 55% likelihood of persistent tumour.

Antagonism of GABA(B) receptors by morpholino-2-acetic acid derivatives Sch 54679 and Sch 51324 in rat brain

In rat neocortical slices maintained in Mg2+-free Krebs medium, baclofen depressed the rate of spontaneous discharges in a concentration-dependent manner (EC50 = 4.5 microM). This depression was reversibly antagonised by 5-(S,R)-hydroxymethyl-5-methylmorpholinyl-2-(R,S)-acetic acid (Sch 54679) and 2-(R,S)-5-[spirocyclopentyl]-morpholinyl-acetic acid (Sch 51324) (respective pA2 values of 5.8+/-0.15 and 5.4+/-0.2). In electrically-stimulated slices preloaded with [3H]gamma-aminobutyric acid (GABA), Sch 54679 (EC50 = 3 microM) was 2.3 times more potent than Sch 51324 (EC50 = 7 microM) in increasing [3H]GABA release through antagonism of GABA(B) autoreceptors. These structurally novel analogues may be pharmacologically useful for elucidating GABA(B) receptor functions.

Tonic activation of presynaptic GABAB receptors in the opener neuromuscular junction of crayfish

Release of excitatory transmitter from boutons on crayfish nerve terminals was inhibited by (R,S)-baclofen, an agonist at GABAB receptors. Baclofen had no postsynaptic actions as it reduced quantal content without affecting quantal amplitude. The effect of baclofen increased with concentration producing 18% inhibition at 10 microM; EC50, 50% inhibition at 30 microM; maximal inhibition, 85% at 100 microM and higher. There was no desensitization, even with 200 or 320 microM baclofen. Phaclofen, an antagonist at GABAB receptors, competitively antagonized the inhibitory action of baclofen (KD = 50 microM, equivalent to a pA2 = 4.3 +/- 0.1). Phaclofen on its own at concentrations below 200 microM had no effect on release, whereas at 200 microM phaclofen itself increased the control level of release by 60%, as did 2-hydroxy-saclofen (200 microM), another antagonist at GABAB receptors. This increase was evidently due to antagonism of a persistent level of GABA in the synaptic cleft, since the effect was abolished by destruction of the presynaptic inhibitory fiber, using intra-axonal pronase. We conclude that presynaptic GABAB receptors, with a pharmacological profile similar to that of mammalian GABAB receptors, are involved in the control of transmitter release at the crayfish neuromuscular junction.

Evaluation of 3-aminopropanesulphonamide analogues of GABA as antagonists at GABA(B) receptors in peripheral and central preparations

Cholinergic twitch responses in the guinea-pig isolated ileum, and spontaneous discharges in rat neocortical slices, were depressed by the GABA(B) receptor agonist baclofen. These actions were reversibly antagonised by the sulphonamide derivatives (R,S)-2-hydroxy-3-phthalimidopropanesulphonamide (HPIPS), 3-amino-N-benzoylpropanesulphonamide (ABPS) and 3-phthalimidopropanesulphonamide (PIPS) which produced rightwards shifts of the baclofen concentration-response curves, with pA2 values ranging between 4.1 and 4.3 in both preparations. From these results, HPIPS, ABPS and PIPS constitute a novel class of antagonists at GABA(B) hetero-receptors.

Morpholin-2-yl-phosphinic acids are potent GABA(B) receptor antagonists in rat brain

The pharmacological properties of morpholin-2-yl-phosphinic acids were evaluated on GABA(B) receptors. In rat neocortical slices maintained in Mg2+-free Krebs medium, baclofen, a GABA(B) receptor agonist, produced a concentration-dependent depression of the frequency of spontaneous discharges with an EC50 of 14 +/- 5.5 microM, which was antagonised reversibly by the morpholin-2-yl-phosphinic derivatives. The order of potency was 3-[(3S,6R)-6-[(cyclohexylmethyl)hydroxyphosphinoylmethyl- morpholin-3-yl]benzoic acid (CGP 76290A) (pA2 = 7.1 +/- 0.05) > its enantiomer 3-[(3R,6S)-6-[(cyclohexylmethyl)hydroxyphosphinoylmethyl]-++ +morpholin-3-yl]benzoic acid (CGP 76291A) (pA2 = 6.8 +/- 0.1) > cyclohexylmethyl-[(2R',5S')-5-(3-nitrophenyl)-morpholin-2-++ +ylmethyl]phosphinic acid (CGP 71978) (pA2 = 6.5 +/- 0.05) > cyclohexylmethyl-[(2R,5S)-5-phenyl-morpholin-2-ylmethyl++ +]phosphinic acid (CGP 71980) (pA2 = 6.3 +/- 0.15) > its enantiomer cyclohexylmethyl-[(2S,5R)-5-phenyl-morpholin-2-ylmethyl++ +]phosphinic acid (CGP 71979) (pA2 = 5.8 +/- 0.1). An open chain analogue of CGP 76290A, CGP 56999A (3-[1(R)-[(3-cyclohexylmethyl-hydroxyphosphinoyl)-2(S)-hydro xypropyl-amino]-ethyl]benzoic acid lithium salt) gave a pA2 of 6.6 +/- 0.2. In GABA(B) receptor binding assays, CGP 71982 (the racemic mixture of CGP 76290A and CGP 76291A), CGP 76290A, CGP 76291A, CGP 71978, CGP 71980 and CGP 71979 had IC50 values against [3H]CGP 27492 binding of 8, 1.85, 69, 124, 326 and 1460 nM, respectively. In electrically-evoked [3H]GABA release from rat cortical slices, CGP 71982, CGP 71978, CGP 71980 and its enantiomer CGP 71979, antagonised GABA(B) autoreceptors with EC150 values of 2.5, 33, 181 and 474 nM, respectively. These compounds form a novel class of potent GABA(B) receptor antagonists.

The morpholino-acetic acid analogue Sch 50911 is a selective GABA(B) receptor antagonist in rat neocortical slices

The pharmacological properties of (+)-(S)-5,5-dimethylmorpholinyl-2-acetic acid (Sch 50911) were evaluated on GABA(B) receptors in rat neocortical slices. The GABA(B) receptor agonist, baclofen, produced a concentration-dependent depression of the frequency of spontaneous discharges in slices maintained in Mg2+-free Krebs medium with an EC50 of 6 microM, reversibly antagonised by Sch 50911 (5, 10 and 25 microM) with an apparent pA2 of 6.0 +/- 0.1. The (-) enantiomer Sch 50910 (500 microM) and the racemic des-methyl analogue Sch 48588 (500 microM) were inactive. In slices preloaded with [3H]GABA, Sch 50911 antagonised GABA(B) autoreceptors, increasing the electrically-stimulated 3H overflow in a concentration-dependent manner, with an IC50 of 3 microM. The maximal effect (148 +/- 10.5%) was found at 10 microM, but at 50 microM the response was reduced to 67 +/- 19%. In contrast, evoked release was unaffected by Sch 50910 (100 microM) whilst Sch 48588 at 100 microM increased the overflow by 51.3 +/- 11.6%. In summary, Sch 50911 is a relatively potent antagonist of considerable potential in studies of GABA(B) receptor function.

GABA(B) receptor antagonism by 7-MBFG, a benzo[b]furan analogue of baclofen, in central and peripheral tissues

(R,S)-4-Amino-3-(7-methylbenzo[b]furan-2-yl)-butanoic acid (7-MBFG), a new benzofuran analogue of the GABA(B) receptor agonist baclofen, has been evaluated for pharmacological activity on GABA(B) receptors in the guinea-pig isolated ileum and rat neocortical slices. 7-MBFG (300 and 500 microM) reversibly antagonized the (R,S)-baclofen induced depression of cholinergic twitch contractions in the guinea-pig ileum and shifted the concentration-response curve for baclofen to the right, in a parallel manner, giving an apparent pA2 value of 3.7+/-0.3. Likewise, 7-MBFG (300 and 500 microM) reversibly blocked the baclofen-induced suppression of spontaneous discharges, in rat neocortical slices maintained in Mg2+ -free Krebs medium, and caused a rightward, parallel shift of the baclofen concentration-response curve, giving an apparent pA2 value of 4.1+/-0.1. The compound 7-MBFG belongs to a novel, new class of antagonist at central and peripheral GABA(B) receptors, in which the antagonist properties reside in the pseudo-aromatic character of their 3-benzo[b]furan-2-yl substituents, and might provide useful leads for further development of GABA(B) receptor ligands.

Surgery as salvage therapy in chemotherapy-resistant nonseminomatous germ cell tumours

OBJECTIVE

To review our experience of surgical staging for residual masses after chemotherapy in patients with nonseminomatous germ cell tumour (NSGCT) and positive tumour markers.

PATIENTS AND METHODS

Of 107 patients with metastatic NSGCTs treated surgically after chemotherapy from 1978 to 1995, 30 (median age 30.5 years, range 20-52) had positive tumour markers. These patients were reviewed and the outcome compared with 77 patients who had normal tumour marker values.

RESULTS

Of the 77 patients with negative markers undergoing surgical/pathological staging, 71 (92%) became continuously disease-free, including 37 of 50 (74%) with viable NSGCT in excised specimens. Seventeen of 30 (57%) with raised marker levels undergoing similar surgery for chemotherapy-resistant tumour became disease-free, including 11 of 22 with viable NSGCT in the excised specimens.

CONCLUSION

Although the outcome after surgery is better in patients with negative tumour markers, it is clear that surgery is curative for patients with localized chemotherapy-resistant masses. There is a need for continued debate on the timing of salvage surgery and subsequent chemotherapy.

3' IgH enhancer elements shift synergistic interactions during B cell development

IgH gene expression is tightly controlled over the course of B cell development, B cell activation, and the subsequent differentiation of these cells into Ig-secreting plasmacytes. There are several transcriptional enhancers that map within and downstream of the IgH locus, and some of these have been clearly implicated in the developmental regulation of IgH gene assembly and expression. While some of the individual enhancers from this locus have been studied extensively, the functional interactions possible among this group of enhancers have been largely unexplored. In the present study, we have measured the transcriptional activities of combinations of enhancers introduced into B-lineage cell lines at several different developmental stages. We detected a developmental progression in which the 3' enhancers are initially inactive, then become strongly active through synergistic interactions, and finally achieve a strong level of activity with little interdependency. The relative contributions of E mu (the intron enhancer) and of the 3' enhancers also change as a function of developmental stage. We discuss these results in light of parallel studies of developmental changes in transcription factor requirements.

The gamma-aminobutyric acid uptake inhibitor NO-711 potentiates 3-aminopropylphosphinic acid-induced actions in rat neocortical slices

In rat neocortical slices maintained in Mg2+-free Krebs medium, the GABAB receptor agonists baclofen and 3-aminopropylphosphinic acid dose-dependently reduced the frequency of spontaneous discharges, 3-aminopropylphosphinic acid being 10 times less potent than baclofen. These were sensitive to the antagonist CGP 52432 (3-[[3,4-dichloro-phenyl)methyl]-amino]propyl](-P-diethoxymethyl)- phosphinic acid) (1, 5 and 10 microM). The GABA uptake inhibitor NO-711 (1-(2-(((diphenylmethylene)amino)oxy)ethyl)-1,2,5,6-tetrahydro-3-+ ++pyridinecarboxylic acid) (5 and 10 microM) produced 2.9 and 9 fold increases in the potency of 3-aminopropylphosphinic acid without affecting baclofen-induced responses. In this study, the low potency of 3-aminopropylphosphinic acid when compared to baclofen, may be attributed to its uptake by NO-711-sensitive GABA transporters.

Differential effects of phosphonic analogues of GABA on GABA(B) autoreceptors in rat neocortical slices

The effects of five phosphonic derivatives of GABA on the release of [3H]-GABA from rat neocortical slices, preloaded with [3H]-GABA, were investigated. Phaclofen and 4-aminobutylphosphonic acid (4-ABPA) increased the overflow of [3H] evoked by electrical stimulation (2 Hz) in a concentration-dependent manner, with similar potencies (phaclofen EC50=0.3 mmol/l, 4-ABPA EC50=0.4 mmol/l). At 3 mmol/l, phaclofen increased the release of [3H]-GABA by 82.6+/-8.6%, and 4-ABPA increased the release by 81.3+/-9.0%. 2-Amino-ethylphosphonic acid (2-AEPA) increased the overflow of [3H] by 46.8+/-10.9% at the highest concentration tested (3 mmol/l). In contrast, the lower phosphonic homologue 3-aminopropylphosphonic acid (3-APPA), and 2-amino-2-(p-chlorophenyl)-ethylphosphonic acid (2-CPEPA), a baclofen analogue, did not modify the stimulated overflow. These results suggest that phaclofen, 4-ABPA and 2-AEPA are antagonists at GABA(B) autoreceptors, the latter being the weakest antagonist, whilst neither 3-APPA nor 2-CPEPA are active at these receptors. Since phaclofen, 4-ABPA and 2-CPEPA are antagonists and 3-APPA a partial agonist/antagonist on GABA(B) heteroreceptors, the lack of effect of 3-APPA and 2-CPEPA on [3H]-GABA release in this study suggests that GABA(B) autoreceptors may be pharmacologically distinct from the heteroreceptors.

A single-centre observational study of surgery and late malignant events after chemotherapy for germ cell cancer

OBJECTIVE

To review the impact of surgical staging after treatment on the late malignant events in an unselected group of patients treated with chemotherapy for germ cell cancer of the testis over the last 16 years.

PATIENTS AND METHODS

The study comprised 256 patients treated between 1978 and 1994 who were reviewed for late relapse and development of second germ cell and non-germ cell cancer.

RESULTS

At diagnosis, 142 patients had clinical stage 2, 30 stage 3 and 84 stage 4 disease; 57 patients relapsed within 20 months of treatment, while late germ-cell cancer relapses (> or = 24 months after treatment) occurred in six patients. Of patients relapsing early or late, 42% and 33%, respectively, received surgery after treatment. Only two of those relapsing late remain progression-free with further treatment. Four patients developed germ cell cancer in the contralateral testis, while six developed second non-germ cell cancers.

CONCLUSION

Late events occurred in 6.2% of 256 patients in this series, from 29 to 141 months after treatment. Given that the late relapse rate of six of 256 (2.3%) is less than the incidence of mature teratoma at routine retroperitoneal lymph node dissection, more patients may eventually relapse. These results suggest that there might be a case to evaluate the use of ultrasonographic surveillance of the retroperitoneum and testis at 5, 10 and 20 years, in addition to extending routine surveillance.

Use of intraperitoneal 5-fluorouracil and chlorhexidine for prevention of recurrence of perforated colorectal carcinoma in a rat model

PURPOSE

Colorectal cancer is a prevalent and mortal disease, resulting in nearly 55,000 deaths in the United States annually. Preoperative or intraoperative spillage of tumor cells because of perforation occurs in up to 10 percent of cases. When this spillage occurs, the chance of recurrence and death is dramatically increased.

METHODS

In an effort to reduce the chance of recurrence and death, we used a rat model to evaluate the efficacies of intraperitoneal 5-fluorouracil and chlorhexidine in reducing the incidence of recurrence. Rats were injected with 10 mg/kg azoxymethane subcutaneously weekly for 12 weeks to induce colorectal cancers. At 20 weeks, subtotal colectomies were performed on rats with colorectal tumors and without peritoneal implants or liver metastases. At the time of surgery, a cut portion of the tumor was placed in the abdomen for 30 minutes; the rats then randomly received peritoneal irrigation with 5-fluorouracil, chlorhexidine, or sterile water (control). Eight weeks postoperatively a necropsy was performed. At that time, obvious and suspected recurrences and the anastomotic area were sampled for histologic evaluation.

RESULTS

Significant differences were seen with chlorhexidine vs. water for gross tumor (P = 0.05) and microscopic tumor (P < 0.05). 5-Fluorouracil showed a greater rate of abscess formation vs. both control and chlorhexidine (P > 0.05).

CONCLUSIONS

Use of chlorhexidine intraperitoneal therapy at the time of the operation for perforated colorectal cancer significantly decreases the frequency of gross tumor recurrence but not total recurrences. Intraperitoneal 5-fluorouracil does not significantly decrease recurrence and may increase the risk of abscess when used intraoperatively.

Actions of thienyl analogs of baclofen at GABA(B) receptors in rat neocortical slices

In rat neocortical slices maintained in Mg2+-free Krebs medium, baclofen and its thienyl analogs, 4-amino-3-(5-chlorothien-2-yl)-butanoic acid (5h), 4-amino-3-(5-methylthien-2-yl)-butanoic acid (5d), 4-amino-3-(5-bromothien-2-yl)-butanoic acid (5f) and 4-amino-3-(thien-3-yl)-butanoic acid (5j) dose-dependently suppressed the spontaneous discharges, antagonised by the GABA(B) receptor antagonist 2-hydroxysaclofen (200 microM). Their relative potencies were baclofen > 5h > 5d > 5f > 5j. These heterocyclic analogs may prove useful as GABA(B) receptor agonists in functional studies.

GABAB receptor antagonism by resolved (R)-saclofen in the guinea-pig ileum

The GABAB receptor antagonist saclofen (3-amino-2-(4-chlorophenyl)propylsulphonic acid) has been resolved by chiral high-performance liquid chromatography. The enantiomer (R)-saclofen, but not (S)-saclofen, reversibly antagonised the (R,S)-baclofen-induced depression of cholinergic twitch contractions in the guinea-pig ileum with an apparent pA2 of 5.3. Also, 2-hydroxy-saclofen was resolved by the same method, its (S)-enantiomer yielding an apparent pA2 of 5.0. This method provides a convenient resolution of these antagonists.

Testis conservation studies in germ cell cancer justified by improved primary chemotherapy response and reduced delay, 1978-1994

OBJECTIVE

To investigate the need for the continued encouragement of early diagnosis of germ cell cancer of the testis, in view of the prevailing cure rate of 95%.

PATIENTS AND METHODS

The study comprised a retrospective review of 453 unselected and previously untreated patients referred to one centre between 1978 and 1984, comparing the delay from first symptoms with the histological diagnosis.

RESULTS

With a delay of < 30 days, 20% of patients had overt metastases at presentation and if the delay was > 4 months. 55% had metastases (chi-squared trend = 15.9, P < 0.001); 18% of Stage-1 patients under surveillance with a delay of < 30 days relapsed, compared with 38% of those with a delay of > 4 months. During the period 1978-1983, 16% of patients were seen after a delay of < 60 days, during the period 1984-1988 the proportion was 22% and during 1989-1994, 31% (chi-squared trend = 8.2, P < 0.004). There was a non-significant trend for a more prolonged delay in those aged < 21 years and > 40 years. Thirty-two patients had chemotherapy with the primary tumour in situ; at orchidectomy, 13 of 18 had no viable malignancy and four of five with viable malignancy also had drug-resistant metastases. Fourteen did not undergo orchidectomy; within a median follow-up of 9 years, one developed a second (histologically different) tumour after 12 years. The outcome of preliminary attempts to use neoadjuvant chemotherapy with or without partial orchidectomy for patients with tumours in a solitary testis is discussed.

CONCLUSION

These findings clearly justify the continued encouragement of early diagnosis, possibly best performed as part of an extended educational programme of genital health at puberty. The long-term potential for testis conservation should be explored initially in tumours in a solitary testis.

3-amino-2-hydroxy-N-(4-nitrophenyl)-propanesulphonamide, a new class of GABAB receptor antagonist in central and peripheral preparations

Racemic 3-amino-2-hydroxy-N-(4-nitrophenyl)-propanesulphonamide (AHPNS), a sulphonamide analog of GABA, reversibly and competitively antagonised the concentration-dependent depression of cholinergic twitch contractions by baclofen, in the electrically stimulated guinea-pig isolated ileum, with a pA2 of 4.0 +/- 0.2. In the rat neocortex, maintained in Mg(2+)-free medium, AHPNS (100-500 microM) also reversibly antagonised the baclofen (10 microM)-induced suppression of spontaneous discharges. AHPNS is a new class of GABAB receptor antagonist that has central and peripheral blocking actions.

Immunoglobulin gene transcription ceases upon deletion of a distant enhancer

The tissue-specific E mu enhancer within the immunoglobulin heavy chain (IgH) locus has recently been shown to be essential for efficient V region gene assembly in early B lineage cells. However, we and others have shown that late stage, Ig-secreting cells can produce IgH in the absence of E mu. In the present study we have explored the notion that another enhancer found in the far 3' region of the IgH locus (3' alpha E) takes on an important regulatory role in cells that have reached this terminal stage in B cell development. The technique of homologous recombination was used to disrupt the 3' alpha E region in an E mu-deficient, Ig gamma 2a-secreting cell line. Loss of 3' alpha E completely abolished Ig heavy chain gene expression, demonstrating that transcription of this gene was dependent upon sequences that reside over 70 kb downstream. The ability of these sequences to function efficiently in the absence of E mu may also provide an explanation for deregulated c-myc expression in many Ig-secreting tumors.

The (S)-enantiomer of 2-hydroxysaclofen is the active GABAB receptor antagonist in central and peripheral preparations

In the guinea-pig isolated ileum, (RS)-(+/-)-baclofen induced a depression of cholinergic twitch contractions, reversibly and competitively antagonised by (S)-2-hydroxysaclofen (pA2 = 5.2 +/- 0.2), but not by (R)-2-hyroxysaclofen. The depression of excitatory field potentials by baclofen ( 5 mu M) in rat CA1 hippocampal slices was antagonised by (S)-2-hydroxysaclofen (100 mu m) (pA2 = 4.3), whilst in rat neocortex, (S)-2-hyroxysaclofen (50-500 mu M) antagonised the baclofen (10 mu M)-induced suppression of spontaneous discharges, the (R)-enantiomer being inactive. These results show that (S)-2-hydroxysaclofen is the active antagonist at central and peripheral GABAB receptors.

Interactions of N-ethylmaleimide and aluminium fluoride with GABAB receptor function in rat neocortical slices

Interactions of N-ethylmaleimide and aluminium fluoride (AlF - 4) with GABAB receptors have been examined using spontaneously discharging rat neocortical slices. The suppression of discharges by the GABAB receptor agonist baclofen (5-10 mu M) was irreversibly prevented by N-ethylmaleimide (10-50 mu M) and its analog N-phenylmaleimide (10-50 mu M), whilst superfusion of slices with NaF (10 mM) and AlCl3 (100 mu M) to form a fluoroaluminate (AlF - 4) complex markedly potentiated the action of baclofen. The lipoxygenase inhibitors, nordihydroguaiaretic acid (10-50 mu M) and eicosatetraynoic acid (10-50 mu M) or the phospholipase A2 inhibitor bromophenacylbromide (50-100 mu M) did not affect the response to baclofen. The depressant action of baclofen is evidently mediated through G-proteins, but is not dependent on arachidonic acid metabolites.

Accelerated cisplatin-based chemotherapy for advanced bladder cancer

The toxicity and efficacy of accelerated cisplatin, vincristine and methotrexate was assessed in patients with advanced urothelial carcinoma. 30 consecutive patients were entered into a phase II trial and treated with cisplatin, vincristine and methotrexate given every 10 days (MOPq10) for four cycles, followed by two further cycles at 21 day intervals. Five complete responses and 14 partial responses were observed (overall response rate 63%; 95% confidence interval 45-78%). The median progression-free survival was 7.5 months (range 1.8-28) and the median overall survival 10.5 months (range 2.36). Toxicity was moderate with no treatment-related deaths. It is concluded that although the overall survival is still disappointing, the toxicity is less with the protocol than reported with methotrexate, vinblastine, doxorubicin and cisplatin (M-VAC) or escalated M-VAC (E-MVAC) and the time on treatment is shorter. MOPq10 provided palliative benefit to two-thirds of patients with advanced transitional cell carcinoma including those in their eighth decade.