Limited proteolysis and 'in vitro' mutagenesis of bovine brain inositol monophosphatase identifies an N-terminal region important for activity

Bovine brain inositol monophosphatase is rapidly cleaved by endoprotease lys-C at a single site in the absence of SDS. Further sites are revealed only after prolonged incubation with high concentrations of protease. The initial cleavage occurs near one end of the enzyme, generating an N-terminally-derived 36-residue peptide, which is blocked, and a large 28 kDa fragment bearing a free N-terminus. The start sequence of this fragment was found to be Xaa-Ser-Pro-Ala-Asp-Leu-Val, consistent with the cDNA sequence, and Lys-36-Ser-37 was identified as the cleavage site. The activity of the cleaved enzyme was markedly decreased to 3% of that of the native enzyme, although its dimeric structure was preserved. The 36-residue peptide was not covalently associated with the large fragment after proteolytic cleavage, although the possibility of non-covalent association could not be excluded. Finally, the epitope for the inhibitory monoclonal antibody G-2A4 [Gee, Howell, Ryan & Ragan (1989) Biochem J. 264. 793-798] was found to lie proximal to the endoprotease lys-C cleavage site. In vitro mutagenesis further mapped the epitope for monoclonal antibody G-2A4 to residues around Cys-8 of the enzyme. These results suggest that the N-terminal region of the enzyme is important for activity.

An electron microscopic evaluation of the enamel surface subsequent to various debonding procedures

In this study, enamel surface roughness was investigated following the use of various combinations of bonding agents, burrs and polishing procedures. Orthodontic brackets were bonded to 135 premolar teeth extracted from adolescents. Subsequent to debonding and finishing, the enamel surface was gold coated and examined in the scanning electron microscope. Each 200x photomicrograph was graded according to surface roughness and assigned to one of four selected standard grades. The use of different composites and different burs showed no significant effect on the finish of the enamel surface using Chi-square tests. Only two finishing procedures had a significant effect on surface roughness. The use of a Soflex disc followed by pumice slurry resulted in the roughest enamel surface and the use of pumice alone produced the smoothest enamel surface.

Effect of sulfhydryl-deficient diets on hepatic metallothionein, glutathione, and adenosine 3'-phosphate 5'-phosphosulfate (PAPS) levels in rats

Low dietary concentrations of methionine and cysteine are known to decrease hepatic glutathione content. However, it is not known if restricting the dietary content of these sulfur containing amino acids also affects hepatic levels of adenosine 3'-phosphate 5'-phosphosulfate (PAPS), the cofactor for sulfation, or metallothionein, a protein rich in sulfhydryl groups. Rats were fed diets lacking cysteine and containing various concentrations of methionine (0.15, 0.3, or 0.6%) for 8 days. Control diet contained 0.3% each of methionine and cysteine. Hepatic glutathione levels were decreased approximately 75% in rats fed diets containing 0.15 or 0.3% methionine. In contrast, PAPS and hepatic metallothionein concentrations were not decreased by the low sulfhydryl diets. Additionally, rats on the various diets were challenged by the administration of ZnCl2 (3 mmol/kg. sc). In both control rats and rats maintained on sulfhydryl-deficient diets, ZnCl2 increased hepatic metallothionein to the same level. However, significantly lower levels of PAPS were observed after ZnCl2 in rats receiving sulfhydryl-deficient diets than in controls. In summary, restriction of dietary sulfhydryl markedly decreases the hepatic content of glutathione and has a minor effect on PAPS concentration, but does not decrease the basal hepatic concentration of metallothionein or its induction by ZnCl2.

A monoclonal antibody to bovine brain inositol monophosphatase. Immunoaffinity purification of the brain and kidney enzymes and evidence for their structural identity

A monoclonal IgG2b(K) antibody, G-2A4, has been generated against bovine brain myo-inositol monophosphatase (EC 3.1.3.25). The identity of the antigen recognized by the antibody was established by using e.l.i.s.a. and Western blotting procedures, and by immunoprecipitation of enzyme activity from crude brain supernatant. In addition, the hydrolysis of Ins1P by crude brain extract was inhibited by up to 83% by the pure antibody. Under identical conditions, the hydrolysis of Ins(1,4)P2 was unaffected. An immunoadsorbent column containing monoclonal antibody G-2A4 covalently attached to CNBr-activated Sepharose 4B has been used for rapid purification of the brain enzyme. Elution conditions have been optimized to allow isolation of the enzyme in high yield (54%) with full retention of column-binding capacity. The enzyme was electrophoretically homogeneous, Mr 30,000 and of higher specific activity than that purified conventionally. Chromatography of the pure enzyme on high resolution ion-exchange columns revealed some charge heterogeneity, possibly indicative of some type of post-translational modification. The immunoadsorbent column has also been used to purify the bovine kidney cortex enzyme to homogeneity. Partial proteolytic fragmentation patterns of the brain and kidney enzymes using endoprotease glu-C were identical, suggesting that they are almost certainly products of the same gene.

Fulminant liver failure and pancreatitis associated with the use of sulfamethoxazole-trimethoprim

We report the case of a 26-yr-old patient with fulminant liver failure and acute hemorrhagic pancreatitis secondary to the use of trimethoprim-sulfamethoxazole (Bactrim DS). Our patient presented with skin rash and decreased C3 and C4 levels, which we believed was due to a hypersensitivity reaction secondary to the sulfonamide component (sulfamethoxazole). To our knowledge, this is the first case reported in which sulfamethoxazole-trimethoprim has been implicated as a cause of fulminant liver failure and acute hemorrhagic pancreatitis simultaneously, and emphasizes the need of discontinuing this medication as soon as there is evidence of liver and pancreatic dysfunction.

Oral hygiene program for orthodontic patients

The gingival and periodontal health of 62 adolescent orthodontic patients was assessed before and again after orthodontic treatment in a controlled clinical study. Before the commencement of orthodontic treatment, the experimental group received an oral hygiene program consisting of 4 weekly sessions of oral health education, instruction on plaque-control techniques and reviews in plaque removal performance. The control group did not receive this program. It was found that there was a general trend in the study population for improved gingival health as measured by the bleeding index, gingival index, plaque index and gingival crevicular fluid volume. Furthermore, the oral hygiene program induced in the experimental group significantly lower scores in the measured clinical indices compared to the control group. However, no significant difference was noted in the measured probing depths in all subjects before or after the study period.

Fulminant idiopathic pseudomembranous colitis

Pseudomembranous colitis is characterized by inflammatory plaques and pseudomembranes on the colonic mucosa. The disorder most commonly occurs after the use of antibiotics, which allow overgrowth of Clostridium difficile, a spore-forming, gram-positive rod that produces a toxin. Overgrowth of Staphylococcus aureus can also produce pseudomembranous colitis. In rare cases, pseudomembranous colitis is not associated with antibiotic use. When C. difficile is present, vancomycin or metronidazole usually produces a prompt response. In idiopathic cases, surgery may be required.

Evidence for at least four different inositol bisphosphatases in bovine brain

Bovine brain supernatant contains at least four enzymes capable of hydrolysing inositol bisphosphates. These activities may be distinguished on the basis of their metal, salt and pH dependence, sensitivity to Li+ ions and thiol-modification reagents, and on their molecular sizes. In addition to Li+-sensitive Ins(1,4)P2/Ins(1,3,4)P3 1-phosphatase [Gee et al. (1988) Biochem. J. 253, 777-782] which has an absolute requirement for Mg2+, two (Li+-insensitive and Mg2+-independent) phosphatases, capable of hydrolysing Ins(3,4)P2 and Ins(1,3)P2, respectively, have been identified. Both enzymes were inhibited by only moderate concentrations of salt, although for the former there was no obvious correlation between inhibitory potency and either the nature of the anion/cation or the ionic strength of the buffer. Ins(3,4)P2 phosphatase had a pH optimum of 7.6 and this activity could be resolved on gel-filtration columns into a two overlapping peaks of molecular mass 170 kDa and 450 kDa. Mg2+-independent Ins(1,3)P2 phosphatase had a pH optimum of 7.1 and displayed a single broad activity peak on gel-filtration columns. However, if assays were performed in the presence of Mg2+, a second Ins(1,3)P2 phosphatase was revealed (35 kDa), which had a pH optimum of 8.8 Ins(1,4)P2/Ins(1,3,4)P3 1-phosphatase, Ins(3,4)P2 phosphatase, Mg2+-independent Ins(1,3)P2 phosphatase and inositol monophosphatase were all inhibited by 5,5'-dithiobis(2-nitrobenzoic acid) with IC50 values of 34 microM, 65 microM and 560 microM and 1100 microM, respectively. The metabolism of Ins(1,3,4)P3 by brain supernatant was also examined. Product specificity was shown to be entirely dependent on the buffer conditions employed. In Mg2+-containing buffers, Ins(1,3,4)P3 was hydrolysed predominantly to Ins(3,4)P2, consistent with hydrolysis by Ins(1,4)P2/Ins(1,3,4)P3 1-phosphatase. In the presence of EDTA, Ins(1,3,4)P3 was degraded exclusively by a 4-phosphatase enzyme generating Ins(1,3)P2. Under these conditions, high concentrations of Ins(3,4)P2 blocked the hydrolysis of Ins(1,3,4)P3.

Effects of high-frequency chest wall oscillation on respiratory control in humans

We studied the spontaneous breathing patterns of 10 normal adult volunteers during high-frequency chest wall oscillation (HFCWO), accomplished by inflating and deflating a vest worn around each subject's thorax at 2.5 Hz. Tidal volumes generated by HFCWO averaged 100 ml. Mean vest pressure was maintained at approximately 35 cm H2O throughout each experiment, even when HFCWO was not applied. During HFCWO, subjects were instructed occasionally to exhale deeply to obtain end-tidal samples representative of PACO2. HFCWO increased the breath-to-breath variability of spontaneous respiration in all subjects, prolonging expiratory pauses and producing short apneas in some cases. PACO2 decreased significantly (p less than 0.05). The effects on minute ventilation, tidal volume, and inspiratory and expiratory durations remained variable across subjects, even when differences in PACO2 between control and HFCWO states were reduced through inhalation of a low CO2 mixture. None of the changes were statistically significant, although average expiratory duration increased by 29%. Ventilatory responses to CO2 with and without HFCWO were also measured. Normocapnic (PACO2 = 40 mm Hg) ventilatory drive increased significantly (p less than 0.05) in six subjects (Type 1 response) and decreased substantially in the others (Type 2 response); with hypercapnia, the changes in drive were attenuated in both groups. Consequently, CO2 sensitivity decreased in Type 1 subjects and increased in Type 2 subjects. A simple analysis based on this result shows that with HFCWO, Type 2 subjects breathing air will tend to have a lower spontaneous minute ventilation and become hypercapnic. Type 1 subjects will become hypocapnic, but minute ventilation may be higher or lower than control.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of diaphragmatic contractility to diaphragmatic blood flow in newborn lambs

We determined the relationship of diaphragmatic contraction rate to diaphragmatic blood flow (Qdi), metabolism, and contractility in nine open-chested mechanically ventilated newborn lambs. The diaphragm was paced for 15 min at slow (20/min) and fast (100/min) contraction rates each followed by a 30-min rest period. There was a mild reduction in transdiaphragmatic pressure (Pdi) during the slow contraction period accompanied by a shift to the right of the curve relating stimulation frequency (10-100 Hz) to Pdi. Pdi returned to control at the start of the fast contraction period, but then fell by 30% within 2 min with continued fast contraction rates. The frequency-Pdi curve was significantly shifted to the right. Qdi, O2 transport, and O2 consumption increased during slow contraction and to an even greater extent during fast contraction. Fractional O2 extraction reached an apparent maximum during slow contraction. Lactate efflux from the right phrenic vein during slow contraction remained unchanged from control. During fast contraction lactate efflux rose proportionately more than did O2 consumption. We conclude that the energy demands at fast rates of diaphragmatic contraction in newborn lambs cannot be met by aerobic metabolism alone despite increasing O2 transport to the diaphragm.

Effect of glutathione depletion on sulfate activation and sulfate ester formation in rats

Sulfation of organic compounds requires activation of inorganic sulfate via formation of adenosine 3'-phosphate 5'-phosphosulfate (PAPS). Inorganic sulfate can be formed by sulfoxidation of cysteine, which can be derived from GSH. Thus, a decrease in hepatic GSH may impair formation of inorganic sulfate, the synthesis of PAPS, and the sulfation of chemicals. This hypothesis was tested by investigating the effect of GSH depletion on the levels of inorganic sulfate in serum and of PAPS in liver, and on the capacity to form the sulfate conjugate of harmol in rats. Phorone (2 mmol/kg, i.p.) decreased hepatic GSH (97%), serum inorganic sulfate (63%), and hepatic PAPS (48%). Diethyl maleate and vinylidene chloride (6 mmol/kg, each, i.p.) were less effective than phorone in decreasing GSH in liver and inorganic sulfate in serum, and they did not alter hepatic PAPS levels. Three hours after phorone treatment, the nadir of hepatic PAPS concentration, harmol was injected in order to assess sulfation in vivo. After administration of harmol (100 and 300 mumol/kg, i.v.), less harmol sulfate and more harmol glucuronide were found in the serum of phorone-treated rats as compared to control rats. At the higher dosage of harmol, phorone reduced the biliary excretion of harmol sulfate while increasing the biliary excretion of harmol glucuronide. These results indicate that severe GSH depletion decreases PAPS formation and sulfation of chemicals. However, an increase in glucuronidation may compensate for the impaired sulfation.

31P-NMR study of resting in vitro rat diaphragm exposed to hypercapnia

We have reported previously that, when exposed to hypercapnia of various intensities, the diaphragm reduces its force of twitch and tetanic contractions in the in vitro rat preparation as well as in the in vivo dog preparation. The experiments reported here with 31P nuclear magnetic resonance (31P-NMR) spectroscopy attempt to examine cellular mechanisms that might be responsible for this deterioration in mechanical performance. Specifically they describe certain characteristics of this preparation and cautions needed to study the resting in vitro rat diaphragm with such techniques. Second, they report the response of intracellular pH (pHi), phosphocreatine (PCr), ATP, and inorganic phosphate (Pi) in the resting in vitro rat diaphragm exposed to long-term normocapnia or to long-term hypercapnia. The results show that 1) to maintain a viable preparation, it was necessary to keep the diaphragm extended to an area approximating that at functional residual capacity, 2) the diaphragm seemed quite capable of maintaining a constant pHi and constant contents of ATP and Pi during normocapnia, but there was a gradual decline in PCr, and 3) during hypercapnia there was a significant decrease in pHi, but the behavior of the phosphate metabolites was exactly as during normocapnia. The results suggest that the decrease in mechanical performance of the diaphragm is probably not due to a decrease in the availability of the high-energy phosphates, although they do not completely exclude this possibility or possibilities related to regional compartmentation.

NMR study of rat diaphragm exposed to metabolic and compensated metabolic acidosis

When exposed to hypercapnia, several muscles deteriorate with respect to their mechanical performance. Exposure to metabolic acidosis and, perhaps surprisingly, to compensated metabolic acidosis has the same effect on the diaphragm. The mechanisms involved in these effects remain unclear. If the diaphragmatic intracellular pH (pHi) is assumed to decrease with hypercapnia, to remain unchanged during metabolic acidosis, and to increase during compensated metabolic acidosis, it would appear that different mechanisms must be responsible for the depreciation in the diaphragm's mechanical performance. The present experiments using 31P nuclear magnetic resonance (31P-NMR) spectroscopy were undertaken to determine the effect of metabolic acidosis and compensated metabolic acidosis on pHi and on high-energy phosphate metabolites in the resting rat diaphragm. A whole diaphragm was slightly stretched while being stitched onto a fiberglass mesh. The area approximated that at functional residual capacity. It was superfused in the NMR sample tube with a phosphate-free Krebs-Ringer bicarbonate solution [( HCO3-] = 6 meqO equilibrated with either 95% O2-5% CO2 or 98.75% O2-1.25% CO2). Spectra were acquired during 15-min intervals for control (30 min of normal Krebs-Ringer bicarbonate superfusate, equilibrated with 95% O2-5% CO2), for 120 min of exposure to either form of acidosis and for 60 min of recovery with normal superfusate. The pHi decreased rapidly during metabolic acidosis but did not change significantly during compensated metabolic acidosis. In both forms of acidosis, phosphocreatine declined gradually but not significantly, whereas ATP and inorganic phosphate did not change at all. The results suggest that HCO3- passes freely through the diaphragmatic sarcolemma, very much like the cardiac sarcolemma.(ABSTRACT TRUNCATED AT 250 WORDS)

Ion chromatographic determination of sugar phosphates in physiological samples

Ion chromatography is shown to be capable of simultaneous determination of biologically important anions. Application of this technique is illustrated for the separation and quantification of the major anions present in rat brain and liver tissues. Sugar phosphates and carboxylic acids are separated on high-performance anion-exchange columns and are detected using chemically suppressed conductivity. Detection limits range from 20 to 100 pmol for the anions tested, including inositol phosphates, lactate, pyruvate, glucuronic acid-1-phosphate, fructose-6-phosphate and glucose-6-phosphate. The coefficient of variation for the determination of most anions was in the range 5-10%. Many of these anions are either difficult to separate with other methods, or require expensive radiochemical techniques for detection. This method should be applicable to other biological studies, from the flow of carbons in photosynthesis to the study of synaptic transmission.

Interaction of fatigue and hypercapnia in the canine diaphragm

We studied 10 open-chest dogs and measured the pressure across the diaphragm (Pdi) in each period of the protocol during stimulation at frequencies of 1, 20, 50, and 80 Hz. Three ranges of arterial PCO2 (PaCO2) were examined: less than or equal to 26, 36-50, and greater than or equal to 89 Torr. The diaphragm was fatigued with repetitive phrenic stimulation (30 Hz). During the fatiguing activity, five of the animals were subjected to hypercapnia and the other five to hypocapnia. A frequency-Pdi curve was generated for each period in the protocol. The data show that 1) fatiguing to 50% of the initial Pdi value during hypercapnia was significantly more rapid than during hypocapnia; 2) both the prefatigue and postfatigue mean Pdi values over all interactions of frequency, fatigue, and PaCO2 were unaffected by the fatiguing environment (hypercapnia vs. hypocapnia); 3) the percent reduction of Pdi by hypercapnia was the same at all four frequencies; 4) hypocapnia did not alter either the pre- or postfatigue frequency-Pdi curve; and 5) one-half relaxation time, unaffected by PaCO2, was prolonged by fatigue. We conclude that the hypercapnic diaphragm has less endurance than the hypocapnic diaphragm and that although both fatigue and hypercapnia decrease Pdi, they appear to be separate entities working through different mechanisms.

Primary structure around the lipoate-attachment site on the E2 component of bovine heart pyruvate dehydrogenase complex

Bovine heart pyruvate dehydrogenase complex was acetylated by using [3-14C]pyruvate in the presence of N-ethylmaleimide, with approx. 1 mol of acetyl groups being incorporated per mol of E2 polypeptide. After peptic digestion, lipoate-containing peptides were purified by high-voltage electrophoresis and ion-exchange and reverse-phase h.p.l.c. The amino acid sequence around the lipoic acid-attachment site of E2 was determined by automated Edman degradation. Acetylation of a lipoate cofactor bound to a lysine residue was verified by fast-atom-bombardment m.s.

Use of nude mouse xenografts as preclinical drug screens: in vivo activity of established chemotherapeutic agents against melanoma and ovarian carcinoma xenografts

To evaluate the utility of nude mouse xenografts as preclinical drug screens, the activity of ten established chemotherapeutic agents was evaluated against seven melanoma and three ovarian carcinoma xenografts. Xenografts were established using primary explants from patients who had not received chemotherapy and serially passaged as sc tumors in nude mice. In vivo drug activities for dactinomycin, carmustine, vinblastine, melphalan, amsacrine, cisplatin, bleomycin, mitomycin, doxorubicin, and etoposide were evaluated by 4 weekly ip injections of 10% less than LD10 doses. Plots of relative tumor growth versus time were nearly log-linear. Analysis of in vivo activity was performed using percent control growth (treated/control tumor volume) and by calculation of a novel growth delay index obtained by fitting growth curves to a quadratic regression model. Both modes of data analysis identified alkylating agents (melphalan, carmustine, and mitomycin) as the most active drugs against human melanomas. Melphalan, mitomycin, and cisplatin showed the greatest activity against ovarian xenografts. However, complete tumor regressions were noted only with melphalan, mitomycin, and cisplatin against a single ovarian tumor xenograft. Correlation analysis suggested xenograft tumor growth rate was an important determinant of drug response. These results suggest that preclinical, new-drug screening with melanoma xenografts would identify drugs such as alkylating agents as active, and may not provide an advantage over murine leukemia screens. However, screening with ovarian xenografts may more closely reflect clinical drug activity. Criteria for detecting active drugs in such systems are discussed.

The preoperative and postoperative investigation of TSH and prolactin release in the management of patients with hyperprolactinaemia due to prolactinomas and nonfunctional pituitary tumours: relationship to adenoma size at surgery

We report here our results of the pre- and post-operative assessment of prolactin and TSH status in 41 hyperprolactinaemic patients who underwent pituitary surgery over a 5 year period. Preoperatively in patients with prolactinomas (n = 33) the TSH response to domperidone decreased with increasing adenoma size. When the data are expressed on a group mean basis the exaggerated TSH response to domperidone in preoperative prolactinoma patients was reduced significantly in patients rendered normoprolactinaemic by surgery but persisted in those who remained hyperprolactinaemic. Similarly the reduced preoperative PRL responses to domperidone and TRH were significantly increased by successful surgery. In contrast patients with stalk-compression hyperprolactinaemia (n = 6) due to larger lesions which were not prolactinomas all showed reduced or absent TSH responses to domperidone. The PRL responses to domperidone and TRH were reduced or absent both in patients with prolactinomas and in those with stalk-compression hyperprolactinaemia. All patients with stalk-compression hyperprolactinaemia showed a delayed pattern of TSH response to TRH with 60 min values being greater than 20 min ones. In contrast a normal pattern of TSH response to TRH was observed in all patients with hyperprolactinaemia due to prolactinomas. Postoperatively TSH and PRL responses were largely unchanged in patients with stalk-compression hyperprolactinaemia regardless of whether normoprolactinaemia was restored by surgery. In conclusion a reduced or absent PRL response to TRH or domperidone is not diagnostic of the presence of a prolactinoma since it occurs in hyperprolactinaemic patients with prolactinomas or stalk-compression. In contrast, the TSH response to acute dopamine antagonism is exaggerated in most patients with small prolactinomas but not in those with stalk-compression hyperprolactinaemia and we have found this to be helpful diagnostically since the presence of an exaggerated TSH response to dopamine antagonism is evidence against the presence of stalk-compression hyperprolactinaemia. The observation of a delayed TSH response to TRH in a hyperprolactinaemic patient should alert the clinician to the possibility of stalk-compression hyperprolactinaemia due to a large lesion which may not be a prolactinoma.

Effects of aminophylline and salbutamol on diaphragmatic force during compensated metabolic acidosis

We investigated the effects of aminophylline and salbutamol on tetanic force generated by the diaphragm during compensated metabolic acidosis in dogs. Anesthetized, mechanically ventilated animals were prepared with an open thorax. A cast was placed around the abdomen to maintain length and geometry of the diaphragm during contractions. A thin-walled latex balloon was positioned beneath the diaphragm to measure transdiaphragmatic pressure (Pdi). Pdi served as the index of diaphragmatic force of contraction. We measured Pdi during supramaximal phrenic stimulation at low and high frequencies and also during spontaneous inspiratory efforts for a constant diaphragmatic EMG activity. Compensated metabolic acidosis significantly reduced Pdi at all stimulation frequencies (p less than 0.05). The mean percent decrease at low frequencies was greater than at high (p less than 0.05). Pdi was decreased during spontaneous contractions as well (p less than 0.05). Administration of aminophylline significantly improved Pdi at all frequencies of phrenic stimulation (p less than 0.05) and during spontaneous inspiratory efforts (p less than 0.05). Infusion of salbutamol did not have a significant effect on Pdi at any frequency of stimulation but did produce a small potentiating effect during spontaneous contractions (p less than 0.05). We also recorded and analyzed the Pdi response to a single supramaximal impulse to the phrenic nerve, referred to as a twitch, to gain insight into possible cellular mechanisms underlying alterations in tetanic force of contraction. Compensated metabolic acidosis led to a significant reduction in peak twitch tension (PTT) (p less than 0.05) and half relaxation time (1/2RT) (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Clonal origin of mouse liver cell tumors

The clonal origin of tumors was studied in a large series of liver cell tumors in mice. Tumors were induced with phenobarbitone alone or following N-nitroso-diethylamine administration in female mice heterozygous for the sparse-fur strain. In this strain, a histochemical technique can be used in heterozygotes to differentiate clearly between liver cells expressing the histochemically positive normal or the histochemically negative abnormal form of the X-linked enzyme ornithine carbamoyl transferase. Three hundred twenty-seven liver tumors in heterozygous female Spf mice were studied: 157 (48%) were uniformly negative, and 160 (49%) were positive (some with partial enzyme loss). One hundred fifty-four liver tumors in normal mice were studied; all were positive, with a frequency of partial enzyme loss similar to that seen in the heterozygotes. Ten (3%) of the tumors in the heterozygotes contained some separate groups of positive and negative cells, but no tumor was made up exclusively of such groups. Even the smallest recognizable tumors were made up of single-phenotype cells, which suggested that a polyclonal origin followed at a later stage by clonal selection was unlikely. It is concluded that at least 97% of the tumors were of single-cell origin, and that convincing evidence of a polyclonal origin was completely lacking. It is also concluded that the histochemical demonstration of an X-linked enzyme in tumors induced in female animals heterozygous for an abnormal form of that enzyme provides an extremely useful technique for the study of the origins of neoplasia.

Management of selected patients with hyperprolactinaemia by partial hypophysectomy

Results are reported in 35 patients with prolactinomas who underwent pituitary surgery within the past five years. After surgery prolactin concentrations became normal in 26 patients and symptoms were alleviated, and nine normal pregnancies were achieved in seven women, including all those who had complained of infertility. Normal prolactin concentrations were restored in 16 of 17 patients with tumours 5-19 mm in diameter but in only six of 11 with tumours less than or equal to 4 mm and four of seven with tumours greater than or equal to 20 mm. Normal prolactin concentrations were restored in all those with preoperative concentrations below 1000 mU/l but in none of those with concentrations above 10 000 mU/l. Although not all of the patients were followed up for five years, hyperprolactinaemia did not recur in any patient whose prolactin concentration had returned to normal six weeks after surgery. This included 16 patients with macroprolactinomas (greater than 10 mm in diameter), who were followed up for from two to five years. These data contrast strikingly with those reported by others at similar stages of follow up and show clearly that partial hypophysectomy offers an acceptable alternative treatment for selected patients with prolactinomas.