Huge Hematoma as First Manifestation of Adrenocortical Carcinoma: A Case Report

BACKGROUND Adrenocortical carcinoma (ACC) is a rare malignancy associated with unfavorable prognosis. It is mainly diagnosed in the fifth or sixth decade of life. Symptoms of ACC are associated with hormonal activity, presence of metastases, and size of the tumor. The treatment and prognosis depend on the stage of the disease assessed with the ENSAT staging system. CASE REPORT A 38-year-old White man was admitted to our department from the city hospital due to a huge hematoma of the right adrenal gland (130×100 mm). On admission, the patient's condition was stable, and no active bleeding or other complications were present. Therefore, initially, conservative treatment was performed. The control CT scan showed reduction of the hematoma (90×80 mm). Due to the unknown character of the tumor and the sudden onset of bleeding, the patient was prepared for elective surgery according to the phaeochromocytoma surgery protocol. Following preparation, the patient underwent right-sided adrenalectomy. In the postoperative histopathological examination, adrenocortical carcinoma was diagnosed, which allowed the patient to receive appropriate oncological treatment. CONCLUSIONS There is currently no clear algorithm for the management of adrenal hemorrhage. A hemodynamically unstable patient requires urgent surgical treatment. Patients in good general condition should be prepared for early elective surgery.

Adrenal-sparing surgery for a hormonally active tumour - a single-centre experience

INTRODUCTION

Surgeries that spare the adrenal cortex during adrenalectomy have profound justification. Indications for this type of surgery are fairly strict, and more than 30 years of observations continuously verify the results of the procedure.

MATERIAL AND METHODS

Of a total of 650 adrenalectomies, 22 (3.4%) were adrenal cortex-sparing surgeries. There were 16 women and six men in this group. In 10 cases, surgery was performed for pheochromocytoma, eight cases involved Conn's syndrome, and in four cases - paragangliomas located in the para-adrenal region. Secretory activity was identified in all cases.

RESULTS

Laparoscopic partial adrenalectomy was performed in 20 patients. Conversion to open laparotomy was necessary in two cases. In patients after bilateral resection of pheochromocytoma surgery, glucocorticoids were supplemented for six weeks. No significant surgical complications were observed in this group.

CONCLUSIONS

Partial adrenalectomy for minor lesions should be a much more commonly utilised treatment method (of choice). Where bilateral adrenalectomy is necessary, a sparing procedure on one side protects patients from the need for hormonal substitution. The remaining part of the adrenal gland undertakes satisfactory secretory function after six weeks at the latest.

Undiagnosed Pheochromocytoma Presenting as a Pancreatic Tumor: A Case Report

Pheochromocytoma is a rare catecholamine-producing tumor of the adrenal gland. Patients with known pheochromocytoma undergoing surgery require preoperative treatment with alpha-blockers to reduce the risk of intraoperative complications related to catecholamine release. If undiagnosed, pheochromocytoma can lead to life-threatening surgical complications. We report the case of a patient with a suspected solid pseudopapillary neoplasm in the pancreatic tail, for whom pancreatoduodenectomy was scheduled. However, shortly after abdominal incision, hypertensive crisis developed and was followed by severe hypotension requiring intravenous vasopressors, which prompted discontinuation of the operation. Further diagnostic evaluation revealed marked elevations in urinary excretion of methylated catecholamines and suggested that the tumor was in fact a pheochromocytoma extending from the left adrenal gland. After preoperative treatment with doxazosin, the patient underwent lateral transperitoneal laparoscopic adrenalectomy, with no major complications and an uneventful postoperative course. The pathological report confirmed a diagnosis of pheochromocytoma. Due to the potential for life-threatening surgical complications in patients with pheochromocytoma not treated preoperatively with alpha-blockers, this tumor type should be included in the differential diagnosis of abdominal tumors of unknown origin.

Surgical treatment of abdominal paragangliomas

INTRODUCTION

Extraperitoneal, abdominal paragangliomas most commonly originate from the sympathetic nervous system. Typical features include catecholamine overproduction and the potential for malignancy. Lesions are usually located paravertebrally, but when growing in a more expansive manner they may also appear between the inferior vena cava and aorta. In the authors' opinion this site excludes laparoscopic tumourectomy.

MATERIAL AND METHODS

Twenty-eight patients were selected for surgical management of abdominal paragangliomas in the past eight years at our endocrine surgical centre. This group consisted of 21 (75%) women and seven (25%) men, aged 14 to 84 years (mean 47.9). In 13 (46.4%) cases paroxysmal hypertension was observed. Type 2 diabetes was noted in another 10 (35.7%) patients, and Takotsubo acute coronary syndrome in two (7.1%). Patients were preoperatively qualified for either open surgery or laparoscopic tumourectomy based on visualisation and location of the tumours in imaging studies.

RESULTS

All patients were successfully operated. Eleven (39.3%) patients qualified for laparoscopy, while the remaining 17 (60.7%) were treated with an open surgical approach due to difficult access to the lesion. The mean operative time was 130 minutes for laparoscopy and 120 minutes for laparotomy (p = 0.2). There were no local or general complications after either type of procedure.

CONCLUSIONS

The use of laparoscopic access is practically excluded in the treatment of paragangliomas located between the inferior vena cava and aorta, especially at the level of the renal vessels and extending superiorly to the diaphragm.

Adrenal Incidentaloma - Diagnostic and Treating Problem - Own Experience

Introduction

Incidentaloma is defined as an tumor diagnosed accidentally using imaging studies performed due to other indications. The aim of this paper was to describe the diagnostic and treatment problems experienced by patients with adrenal incidentaloma in a clinical practice.

Material and methods

In years 2009-2012 there were 33(16,5%) adrenal tumors diagnosed incidentally out of 200 cases treated due to adrenal pathology. The group consisted of 54 patients aged 27-77. In 15(45,5%) patients the diagnosis was made based on ultrasound examination, while in 18(54,5%) the tumor was visualized in CT/MRI.

Results

Only after the diagnostics was finalized, in which in all cases no signs of hormonal activity were detected, 26(78,8%) patients were qualified for the surgery. In 7(21,2%) cases no indications for such a management were found. The latter group was followed-up and in all patients the indications for the surgery arose due to enlargement of the tumor or/and the existence of hormonal activity. Our observations suggest that the incident finding of adrenal tumor is an indication of long-term observation. The analysis of our material shows that all patients observed needed surgical treatment.

Conclusions

The small adrenal tumors under follow-up have a tendency to enlarge and acquire hormonal activity. Long-term observation significantly increases the costs of treatment in that group, which eventually results in surgical management.

Comparison of phenoxybenzamine and doxazosin in perioperative management of patients with pheochromocytoma

BACKGROUND

Adrenalectomy with preoperative pharmacological preparation is strongly recommended in patients diagnosed with pheochromocytoma, in order to prevent perioperative complications.

AIM

To compare phenoxybenzamine (PhB) and doxazosin (DOX) in terms of perioperative haemodynamic status in patients with pheochromocytoma, who have been prepared for adrenalectomy.

METHODS

Retrospective analysis of 44 patients with pheochromocytoma (aged 16-80 years, 29 females) who underwent adrenalectomy. Patients were divided into two groups: 35 patients on DOX and nine patients on PhB.

RESULTS

Mean time of preparation for surgery was 38.8 days in the DOX group and 18.3 days in the PhB group (p = 0.04). No statistically significant differences between the DOX and PhB groups in intraoperative blood pressure (BP) fluctuations were found: < 170/100 mm Hg (34% vs. 44%, respectively, p = 0.42), ≥ 200/110 mm Hg (40% vs. 22%, respectively, p = 0.28). Mean greatest intraoperative systolic BP (195 ± 53 vs. 166 ± 42 mm Hg, p = 0.21) and diastolic BP (98 ± 20 vs. 89 ± 46 mm Hg, p = 0.21), and mean lowest intraoperative systolic BP (87 ± 13 vs. 79 ± 17 mm Hg, p = 0.25) and diastolic BP (49 ± 8 vs. 46 ± 12 mm Hg, p = 0.60) were not different between the DOX and PhB groups, respectively. Sodium nitroprusside was administrated in 30% DOX vs. 11% PhB patients (p = 0.25). Laparoscopic surgery was conducted in 97% DOX vs. 89% PhB patients (p = 0.64). Postoperative BP drop below 90/60 mm Hg was noted in 48% of the DOX vs. 43% of the PhB group (p = 0.56). Negative correlation was found between the length of DOX administration with maximal intraoperative systolic BP (r = -0.45, p = 0.006) and diastolic BP (r = -0.39, p = 0.019).

CONCLUSIONS

There are no clinically relevant differences between patients with pheochromocytoma, who have been prepared for adrenalectomy with DOX or PhB.

The usefulness of laparoscopic adrenalectomy in the treatment of adrenal neoplasms - a single-centre experience

INTRODUCTION

Adrenal neoplasms comprise about 10% of all tumours affecting this organ and constitute a significant, at first diagnostic and subsequently therapeutic, problem, especially since a relatively high proportion of neoplastic lesions are asymptomatic. The number of diagnosed metastases to adrenal glands is increasing. Surgical treatment involves both open surgery as well as laparoscopy.

MATERIAL AND METHODS

There were 245 adrenalectomies performed at our centre due to various indications over the past four years. In 27 (11.5%) cases neoplasms were diagnosed in the final histopahtological examination. In 11 (40.7%) cases primary adrenal cortex tumours were diagnosed, metastases from other solid organ tumours were identified in another 12 (44.4%) patients, and rarer neoplasms were diagnosed in the remaning 4 (14.8%) subjects. Cases of malignant pheochromocytoma were not included in this report.

RESULTS

Laparoscopic adrenalectomy was performed in 23 (85.2%) subjects, while the ramaining 4 (12.9%) patients were subject to open adrenalectomy (conversion to open procedure in one case). There were no deaths or significant complications in the perioperative period. Comparing mean duration of open (140 minutes) and laparoscopic (190 minutes) procedures yielded a statistically significant difference (p = 0.02). There was no statistically significant difference found in the duration of operation with regard to laparoscopic adrenalectomies of tumours less than 50 mm and over 55 mm in diameter (p = 0.16).

CONCLUSIONS

Laparoscopic adrenalectomy is a safe and effective method of treatment of adrenal tumours. Its oncological completeness is comparable (to open surgery) when performed by experienced surgical teams. Laparoscopy is the reason for the smooth postoperative course observed in most patients.

Intravascular Treatment of Left Subclavian Artery Aneurysm Coexisting with Aortic Coarctation in an Adult Patient

Coexistence of aortic coarctation with aneurysm of subclavian artery is a uncommon situation and may require unusual treatment in patients. A 40-year-old patient diagnosed incidentally with left subclavian artery aneurysm coexisting with aortic coarctation. Patient was initially referred for hybrid treatment. Initially ostium of the left subclavian artery was covered with a stent-graft. Over a 30-month follow-up period aneurysm became thrombosed all the way up to the ostium of internal mammary artery. The patient did not present with neurological symptoms or signs of upper limb ischemia. Taking into consideration good blood supply to the axillary artery via reversed blood flow in the thyreocervical trunk, hence we decided not to proceed with cervicoaxillary bypass grafting. Implantation stent-graft into aorta coarctation with covering axillary artery is proper way of treatment and may need no other surgical procedures.

[Not Available]

Among patients undergoing radical cystectomy for muscle-invasive bladder cancer, local and distant recurrence is the main reason for cancer-related deaths. In case of adrenal location of metachronous metastases, the standard treatment consists on cisplatin-based systemic chemotherapy. While surgical removal of metastasis remains controversial approach, more and more data support such treatment as effective and safe. We report two cases of patients submitted to laparoscopic adrenalectomy as a sole treatment mode due to metachronous metastases of bladder cancer. No adjuvant systemic therapy was implemented. After a follow-up of 12 months patients remain disease free. This report is another voice in the on-going debate on the role of surgical treatment of patients with metastatic bladder cancer.

Laparoscopic treatment of adrenal cysts--own research and literature review

MATERIAL AND METHODS

Over the last 18 months we operated on six patients with large adrenal gland cysts in our centre. This consisted of 8.2% of all patients treated in said period due to adrenal gland pathologies. On ruling out malignancy or parasitic nature of the lesions, all patients were surgically treated in order to excise the cysts while leaving the gland untouched. In five patients the cysts were resected but the adrenal gland was spared. However, in one patient the adrenal gland coated the entire cystic mass, which imposed performance of adrenalectomy in addition to cystectomy. During surgeries we tried not to clip the suprarenal vein, which we managed to do in four out of six cases.

RESULTS

A one-year remote follow-up period revealed no cyst recurrence in ultrasound or CT, and it was possible to visualise the remaining part of the adrenal gland in all cases.

CONCLUSION

Thus, in our opinion resection of benign cysts is well justified and recommendable.

The local spread of pheochromocytoma after adrenalectomy with a rupture of the tumor capsule at the time of the surgery

Introduction

We present a case of a 29-year-old patient treated due to fully symptomatic pheochromocytoma of the right adrenal gland.

Case presentation

Patient was operated on and an open right-sided adrenalectomy was performed. At the time of the surgery, a rupture of the tumor capsule occurred. Five years post-operatively, a recurrence of the symptoms of chromaffin-cell tumor was noted. After the exact localization of the multiple recurrences, the patient was reoperated on.

Conclusion

The case of pheochromocytoma is presented due to the possibility of chromaffin-cell seeding into the peritoneum, with no signs of distal metastases so far.

The effect of surgical treatment of phaeochromocytoma on concomitant arterial hypertension and diabetes mellitus in a single-centre retrospective study

INTRODUCTION

Phaeochromocytoma is one of the numerous causes of secondary hypertension. Furthermore, phaeochromocytoma may first present with type 2 diabetes mellitus. The objective of our study was to evaluate the effects of adrenalectomy on patient recovery with regards to normotension and well-controlled glycaemia.

MATERIAL AND METHODS

The retrospective analysis involved 67 patients with phaeochromocytoma operated between 2006 and mid-2012. The pre-operative diagnoses were made in the departments of internal medicine and endocrinology. Based on laboratory tests and diagnostic imaging, we were able to confirm the diagnosis of phaeochromocytoma in 42 (62.7%) patients. We verified the influence of adrenalectomy on the level of patient recovery, with regards to normotension and glycaemic control: arterial pressure and fasting glycaemia levels were obtained on the day of hospital discharge, at follow-up 3 months post-operatively and 1 year after surgical intervention.

RESULTS

Of the 67 patients operated for phaeochromocytoma, 48 (71.6%) were treated laparoscopically, whereas 19 (28.4%) underwent open adrenalectomy. Arterial hypertension was recorded in 53 (79.1%) cases. Furthermore, among this group, diabetes mellitus coexisted in 21 (31.3%) cases. Postoperatively, 70% of cases of arterial hypertension and 90% of type 2 diabetes mellitus were cured. Additionally, a high rate of patients reported a quantitative reduced use of antihypertensive medicines.

CONCLUSIONS

In the majority of patients, surgical treatment of symptomatic phaeochromocytoma leads to a regression of arterial hypertension, or a reduction of the number or doses of medicines taken in one's treatment, and glucose-intolerance symptoms.

A spontaneous paraganglioma-pheochromocytoma syndrome

We present a case of a 40–year old woman diagnosed with a four–place spontaneous paraganglioma–pheochromocytoma syndrome, which was treated surgically. The presence of the succinate dehydrogenase complex subunit D (SDHD) mutation that causes the pheochromocytoma was confirmed but no mutations in the family members were found. After the excision of the paragangliomas located in the areas of the division of carotid arteries, and mediastinum, as well as a tumor on the left site of the celiac trunk, the patient remains asymptomatic and is regularly followed–up.

A novel fragment derived from the beta chain of human fibrinogen, beta43-63, is a potent inhibitor of activated endothelial cells in vitro and in vivo

BACKGROUND

Angiogenesis and haemostasis are closely linked within tumours with many haemostatic proteins regulating tumour angiogenesis. Indeed we previously identified a fragment of human fibrinogen, fibrinogen E-fragment (FgnE) with potent anti-angiogenic properties in vitro and cytotoxic effects on tumour vessels in vivo. We therefore investigated which region of FgnE was mediating vessel cytotoxicity.

METHODS

Human dermal microvascular endothelial cells (ECs) were used to test the efficacy of peptides derived from FgnE on proliferation, migration, differentiation, apoptosis and adhesion before testing the efficacy of an active peptide on tumour vasculature in vivo.

RESULTS

We identified a 20-amino-acid peptide derived from the beta chain of FgnE, beta43-63, which had no effect on EC proliferation or migration but markedly inhibited the ability of activated ECs to form tubules or to adhere to various constituents of the extracellular matrix - collagen IV, fibronectin and vitronectin. Furthermore, our data show that beta43-63 interacts with ECs, in part, by binding to alpha(v)beta(3), so soluble alpha(v)beta(3) abrogated beta43-63 inhibition of tubule formation by activated ECs. Finally, when injected into mice bearing tumour xenografts, beta43-63 inhibited tumour vascularisation and induced formation of significant tumour necrosis.

CONCLUSIONS

Taken together, these data suggest that beta43-63 is a novel anti-tumour peptide whose anti-angiogenic effects are mediated by alpha(v)beta(3).

The Influence of Depleted Glutathione Levels on the Photodynamic Action of Zinc Phthalocyanine in CHO K1 Cells

OBJECTIVE

The current study focuses on any influence that depletion of endogenous glutathione in CHO K1 cells may have on the photodynamic action of zinc phthalocyanine (ZnPc).

MATERIALS AND METHODS

Two lasers--a HeNe laser, 632.5 nm, maximum power output 3.5 mW, and a Toshiba semiconducting laser, 670 nm, maximum power of 7 mW--were used. Chinese Hamster Ovary cells (CHO K1) were exposed to light, 2-10 J. Cellular reduced glutathione levels [GSH] were depressed prior to exposure to ZnPc and laser light, using buthionine sulphoximine, a potent inhibitor of gamma-glutamylcysteine synthetase. The influence of hypoxic intracellular conditions was studied by reduction of oxygen content of cells by 80% following purging of cell cultures with nitrogen.

RESULTS

In well-aerated cells, doubling times are reduced by the photodynamic action of ZnPc by 29 +/- 6%, fig 2 (p = 0.01). Cells with lowered [GSH] do not show this effect (p = 0.1). When hypoxic cells are studied at normal [GSH], no photodynamic effect is observed (p = 0.1). When cell viability is studied, using the 670-nm laser, a photodynamic effect is observed, (80% fall from controls, p < 0.001), irrespective of the cellular [GSH] level for a single dose of 6 J. This effect is observed in cells with normal [GSH], for varied doses of 2 J and higher (63% fall at 2 J, p < 0.001).

CONCLUSIONS

Lowered [GSH] was observed to depress the photodynamic effect of ZnPc when cell-doubling times were the endpoint. The photostimulating effect of ZnPc was similarly suppressed by hypoxic conditions. When cell viability was the endpoint, then a photodynamic effect of ZnPc was observed irrespective of the endogenous [GSH] values.

Photodynamically induced changes of acetylcholinesterase activity from human erythrocytes

The light and photodynamic actions on acetylcholinesterase activity from human erythrocytes were studied. After light irradiation (670 nm, semiconducting low power laser) the maximum reaction rate increased from 13.3 to 14.8 mumol per ml packed cells per min for an energy dose 9 J, and above that dose it decreased (10.8 mumol per ml packed cells per min for an energy dose of 15 J). The Michaelis-Menten constant changed in the opposite direction. After irradiation of erythrocyte suspension in the presence of zinc phthalocyanine the reaction rate increased, reaching the maximum for energy dose of 0.75 J (16.85 in comparison to the control value of 14.7 mumol per ml packed cells per min. Similarly, the Michaelis-Menten constant decreased reaching a minimum for an energy dose of 0.75 J (0.04 mM compared to 0.07 mM for control). Incubation of erythrocytes with the dye in the dark increased the reaction rate from 13.3 to 14.7 mumol per ml packed cells per min. Neither the incubation in the dark nor irradiation with laser light caused changes of enzyme activity in the presence of chloroaluminium or metal-free phthalocyanine.

Effect of combined treatment with perindoprilat and low-power red light laser irradiation on human erythrocyte membrane fluidity, membrane potential and acetylcholinesterase activity

Erythrocyte membrane fluidity, membrane potential and acetylcholinesterase activity were estimated after in vitro combined treatment of human erythrocytes with perindoprilat and low-power red light irradiation. Membrane fluidity was determined using fluorescent labels spectroscopy; membrane potential was evaluated by means of potential-sensitive fluorescent dyes; and acetylcholinesterase activity was estimated using the Ellman method. Both perindoprilat and laser irradiation, when used separately, increase microviscosity in the polar region and hyperpolarize the membranes in comparison with control erythrocytes. The combined action of these agents does not cause any further change in these parameters. Perindoprilat has an additional inhibitory effect on the activity of acetylcholinesterase, whereas laser irradiation causes an increase in the activity of the enzyme. Their combined action restores the initial activity of the enzyme independently of the sequence of treatment with both agents.

Interaction of perindoprilat with human red blood cells

The effects of perindoprilat on the morphology and dynamic properties of human erythrocytes were studied by light microscopy, electron spin resonance spectroscopy and spectrophotometric methods. Erythrocytes were exposed to perindoprilat at 37 degrees C for 30 and 120 min. It was shown that the drug at a concentration of 0.75 microg/ml did not cause significant changes in the structure of erythrocyte membranes. Higher doses of the drug (7.5 and 75 microg/ml) induced changes in membrane fluidity in the hydrophobic core of the lipid bilayer, the conformation of membrane proteins, the number of SH groups and the activity of membrane-bound acetylcholinesterase (AChE). These modifications were accompanied by changes in the shape of erythrocytes and did not depend on time of incubation. Therefore, it is proposed that perindoprilat perturbs the lipid bilayer and disturbs the organization of the protein-lipid environment.

Acetylcholinesterase activity of normal and diabetic human erythrocyte membranes: the effect of oxidative agents

The activity characteristics of membrane acetylcholinesterase from red blood cells of diabetic patients are very different from those of healthy donors: the limiting enzyme reaction rate is 17.2 +/- 0.8 mumol acetylthiocholine per ml packed cells per min compared with 13.1 +/- 0.8 mumol for control cells. This Michaelis constants for substrate are the same: 0.061 +/- 0.007 mM for diabetic and 0.061 +/- 0.004 mM for control cells. Cell exposure to oxidative agent (t-butyl hydroperoxide) significantly changes the enzyme activity parameters. The limiting enzyme reaction rate increases but the affinity for the substrate decreases at lower oxidant concentrations (up to 0.1 mM for the "diabetic" erythrocytes and up to 0.4 mM for the control ones). At higher oxidant concentrations both the limiting reaction rate and the Michaelis constant decrease. The susceptibility of erythrocyte membranes of diabetic patients to oxidative stress is much higher in comparison with control erythrocyte membranes.

Pyrimidine ribonucleoside phosphorylase activity vs 5- and/or 6-substituted uracil and uridine analogues, including conformational aspects

The pyrimidine ribonucleoside phosphorylase from Salmonella typhimurium phosphorylyses 6-methyluridine, a uridine analogue sterically constrained to the syn conformation about the glycosylic bond, as effectively as uridine itself. In conjunction with the observation that 3-methyluridine is a very poor substrate compared to 5-methyluridine and 5,6-dimethyluridine, it follows that the phosphorolysis reaction involves the initial conversion of uridine, and other 5-substituted uridines (including 5-fluorouridine), to the syn conformation during interaction with the enzyme. Furthermore, and consistent with the foregoing, the enzyme recognizes as substrates, to varying degrees, the N(3)-ribosides of xanthine and uric acid, and will also catalyze the formation of these ribosides from the corresponding purines, which may be considered formally as 5,6-disubstituted uracils. Similar observations are reported for the synthetic 5,6-trimethyleneuridine. The enzyme does not, however, recognize 6-methyluracil and 5,6-tetramethyleneuridine in the reverse, synthetic, reaction. The conformational aspects of these reactions are discussed. Since it was previously shown that 6-methyluridine is an equally effective substrate for the pyrimidine phosphorylase of primary rabbit kidney cells, at least some of these conformational requirements apply to the enzyme from mammalian sources, and are consequently of relevance in the design of chemotherapeutic agents, for which some examples are cited.

Pyrimidine nucleoside analogues as inducers of pyrimidine nucleoside catabolizing enzymes in Salmonella typhimurium

Various structural analogues of cytosine and uracil nucleosides were tested as potential inducers of the nucleoside catabolizing (cyt) enzymes in Salmonella typhimurium. Some analogues, e.g. 5'-O-alkyl cytidines and uridines, resistant to catabolic enzymes, were as effective as the natural inducers cytidine and uridine; but etherification of one of the cis 2' or 3'hydroxyls fully abolished activity, pointing to a requirement of an intact ribose cis-glycol system for activity. A uridine analogue in the syn conformation, 6-methyluridine, a good substrate for uridine phosphorylase, was inactive as an inducer. The behavior of various other analogues, in relation to their structure, conformation and substrate properties, indicated the absence of any correlation between inducing activity and substrate susceptibility. The overall findings are consistent with conclusions derived from genetic experiments. The active analogues apparently act via similar pathways, and probably affect the same regulatory mechanism(s) as the natural inducers.

Photochemical transformation of 5-alkyluracils and their nucleosides

Irradiation at 254 nm of aqueous solutions of 5-ethyl-, 5-propyl-, and 5-isopropyluracils (or their nulcleosides) leads to cleavage of the 5-alkyl substituents, via an intramolecular electrocyclic photoaddition intermediate, with formation of uracil (or its nucleoside). The plhotoaddition intermediates represent a new class of dihydropyrimidines, namely analogs of 5,6-dihydro-5,6-cyclobutanyluracil and its nucleosides; the biological significance is discussed.