[Breaking of bad news. Practical advice to physicians for successful communication with patients]

BACKGROUND

In the more and more complex world of modern medicine, communication skills become increasingly important. Many physicians are however unaware of their difficulties in giving information in a clear and comprehensible way. This is especially true for breaking bad news. Keys for good communication consist in: careful preparation of the physical context of the interview; finding out how much the patient knows or suspects; giving the information in small amounts and a balanced way; responding to the patient's feelings and finally making a contract for the future.

Long-term follow-up of endoluminal grafting for aneurysmal and occlusive disease in the superficial femoral artery

PURPOSE

To examine the long-term outcome of patients treated with endoluminal grafts (ELGs) for aneurysmal and occlusive disease in the femoropopliteal (FP) segment.

METHODS

ELGs of radially expandable polytetrafluoroethylene with terminal Palmaz stents were used to form intimal conduits to revascularize lengthy occlusive disease and exclude aneurysms in the FP segment. Patient records were reviewed retrospectively for outcome.

RESULTS

Fifty-five (98%) of 56 ELGs were placed successfully in 51 patients treated from August 1993 to February 1996. Over a mean 36-month follow-up, 28 (50%) ELGs occluded. Half of these failures reflected early technical difficulties. There were 11 (20%) stent stenoses, 6 in the proximal stent and 5 in the distal device. The majority of the graft failures were treated with endovascular techniques; however, FP bypass was required in 7 (25%) patients, while 2 (7%) were not treated. Life-table analysis demonstrated 46% primary and 68% secondary patency rates at 24 months. Among demographic and procedural variables, only previous dilation or stent procedures in the target artery was associated with failure (p < 0.0001).

CONCLUSIONS

The prototype ELG used in this series demonstrated durability similar to conventional surgical therapy utilizing synthetic material. Endoluminal grafting of FP lesions may be a more durable alternative to classical bypass once devices and techniques are refined.

Neuroglial activation repertoire in the injured brain: graded response, molecular mechanisms and cues to physiological function

Damage to the central nervous system (CNS) leads to cellular changes not only in the affected neurons but also in adjacent glial cells and endothelia, and frequently, to a recruitment of cells of the immune system. These cellular changes form a graded response which is a consistent feature in almost all forms of brain pathology. It appears to reflect an evolutionarily conserved program which plays an important role in the protection against infectious pathogens and the repair of the injured nervous system. Moreover, recent work in mice that are genetically deficient for different cytokines (MCSF, IL1, IL6, TNFalpha, TGFbeta1) has begun to shed light on the molecular signals that regulate this cellular response. Here we will review this work and the insights it provides about the biological function of the neuroglial activation in the injured brain.

Development of endoscopic dissection of perforating veins and fasciotomy for treatment of chronic venous insufficiency

As the subfascial endoscopic perforator vein surgery (SEPS) has become increasingly popular, it becomes important to trace the development of this procedure first initiated in 1985. (Improvements in the technique and modifications of initial instrumentation have occurred. These changes are based on experience with greater than 1000 patients treated since 1980 at Krankenhaus der Barmherzigen Brüder in Munich, Klinikum Merheim in Cologne, and the Weilheim Hospital. Results obtained in 96 patients (140 legs) were examined retrospectively and are presented as well as the prospective evaluation of 39 patients with 56 operated legs. (Hauer G, Vasa 1985, 14:59-61; Hauer G, Barkun J, Wisser I, Deiler S, Surg Endosc 1988, 2:5-12; Schneidemann B, Inaug Diss, 1985). This report details the fact that in using our own instruments, including a specially designed videoscope, it has been possible to approach perforating veins of the medial anterior and posterior compartments. This can be done through a 2 cm incision in the proximal calf. Using these instruments, it has been possible to perform a fasciotomy under direct vision. This summary emphasizes that it is not necessary to locate perforating veins preoperatively, and that wound infection and recurrent ulcerations do not occur. This allows application of the method to patients with open ulcers. Further, this report emphasizes that patients with combined arterial and venous ulceration require arterial reconstruction rather than perforator vein interruption. The SEPS operation is relatively contraindicated if there is widespread necrosis and infection of the fascia, especially in combination with ankle ankylosis. In addition, this is the method of choice in patients with multiple incompetent perforating veins with or without open venous ulceration.

Cultivation and characterization of a new immortalized human hepatocyte cell line, HepZ, for use in an artificial liver support system

The new human hepatocyte cell line HepZ was investigated with regard to use it for a mass cell cultivation. The cells were originally derived from a human liver biopsy and immortalized through lipofectamine-mediated transfection of albumin-promotor-regulated antisense constructions against the negative controlling cell cycle proteins Rb and p53 (pAlb asRb, pAIb asp53). Furthermore, plasmids including genes coding for the cellular transcription factor E2F and D1 cyclin (pCMV E2F, pSV2neo D1) were cotransfected to overcome the G1-restriction point. Cell cultivation was performed in a 2-liter bioreactor with a working volume of 1 liter. With CultiSpher G microcarriers used in a concentration of 3 g/l a maximal density of 7.1 x 10(6) cells/ml was achieved in a cultivation period of 20 days. The cells exhibited a maximal specific growth rate of 1.0 per day in the first 4 days. After 9 days of cultivation the stationary growth phase was reached with an average cell density of 5.5 x 10(6) cells/ml. The viability status of the culture was determined indirectly by measuring of the lactate dehydrogenase activity (LDH) at 37 degrees C. During the growth phase the activity rose slightly up to a value of 200 U/l. The cells were flat after first attachment on the gelatine microcarriers and spherical after growing into the three-dimensional inner matrix--both of which characteristics were verified by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The liver-specific cytochrome P450 activity was challenged with a pulse of 7 micrograms/ml lidocaine at a cell density of 4.5 x 10(6) cells/ml. After an induction period of 3 days with 50 micrograms/ml of phenobarbital, 26 ng/ml MEGX were generated within one day compared to 5 ng/ml without induction. The new cell line HepZ has proven to retain liver-specific qualities and to be appropriate for mass cell cultivation for bioartificial devices.

Regulation of the LIM-type homeobox gene islet-1 during neuronal regeneration

Peripheral nerve lesion leads to prominent changes in gene expression in the injured neurons, a process co-ordinated by transcription factors. During development the transcription factor islet-1 plays an important role in differentiation and axogenesis. In axotomized adult neurons a process of axonal regrowth and re-establishment of the neuronal function has to be activated. Thus, we studied changes in the expression of islet-1 after axotomy, under the assumption that frequently developmentally regulated factors are reactivated during neuronal regeneration. We investigated the regulation of islet-1 expression with (i) semi-quantitative reverse transcription polymerase chain reaction and (ii) confocal microscopy in combination with quantitative image analysis. Islet-1 expression was suprisingly down-regulated in motoneurons and sensory neurons of adult rats after axotomy. A maximal reduction in the expression level was reached between day 3 and 7 after nerve lesion, a period of extensive axonal sprouting. Islet-1 expression attained control level at day 42 after lesion, a time-point at which target reinnervation takes place. The decreased expression of islet-1 during axonal regeneration is in contrast to the high levels of islet-1 expression during axogenesis in the developing nervous system. Thus, the proposed role of islet-1 in axonal target finding during axogenesis could not be confirmed in the adult rat. The observed down-regulation of islet-1 rather suggests that the activation of downstream genes important for the embryonic pattern of axonal path finding is suppressed. Moreover, in the adult nervous system islet-1 might be one of the transcription factors regulating the expression of proteins significant for the physiological intact neuronal phenotype.

Stenting for atherosclerotic occlusive disease of the subclavian artery

The purpose of this study was to evaluate the results of stenting subclavian artery pathologic lesions. Between July 1991 and December 1995, 69 patients (36 males: mean age 67 years, range 34-87 years) underwent intraluminal balloon dilatations followed by stent implantations in 70 subclavian arteries to treat primary atherosclerotic stenoses > 70%. Twenty-three patients (34%) were treated for vertebrobasilar insufficiency (VBI), 25 patients (36%) were treated for upper limb ischemia (ULI), and 10 patients (15%) were treated for both VBI and ULI. Other indications included symptomatic subclavian steal phenomenon (SSS), protection of dialysis arteriovenous fistula, coronary steal syndrome, protection of axilloaxillary bypass, distal embolization, and protection of left internal mammary artery (LIMA)-coronary bypass. Fifty-three cases (78%) were treated for stenosis and 17 cases (22%) for total occlusion of the origin of the subclavian artery. The results of this series indicate that stenting of subclavian artery stenosis appears safe and feasible with good short and mid-term patency, improving at those intervals the initial disappointing reports of balloon angioplasty alone. However, its long-term durability is at present unknown.

Renal artery stenosis treated with stent deployment: indications, technique, and outcome for 108 patients

From January 1993 to May 1996, 108 patients (64 men, 44 women; mean age, 72 years; age range, 37 to 87 years) underwent 125 percutaneous transluminal angioplasties and stent implantations primarily for atherosclerotic lesions of the renal artery. Sixty-four patients underwent treatment for renovascular hypertension (two antihypertensive medications or more), 32 patients underwent treatment for a combination of hypertension and renal failure (serum creatinine level >/=1.6 mg/dL), and a small group of six patients (5%) without hypertension or diminished renal function underwent treatment to prevent the progression to renal artery occlusion and kidney loss. Thirty-three patients (31%) had renovascular hypertension that was classified as severe on three or more medications, 31 patients (29%) had renovascular hypertension that was classified as moderate on two medications, and 38 patients (35%) had renovascular hypertension that was classified in the mild group on a single antihypertensive agent. Stenotic lesions were located at the ostium of the renal artery in 82 cases (65%) and were ostial-adjacent (<5 mm from renal ostium) in the other 43 cases (34%). A total of 125 stents were deployed in 125 arteries (procedural success 97.6%). Renovascular hypertension either was cured or was improved in 73 patients (68%), with 14 patients (13%) considered cured (normotensive on no medications). The conditions of 29 patients (27%) were unchanged, and 6 patients (5%) had worsening hypertension after surgery. We were unable to demonstrate a statistically significant improvement in serum creatinine levels after renal artery balloon angioplasty/stenting. Complications occurred in a total of nine cases (7.2%), six of which were related to technical problems. One patient had worsening renal insufficiency caused by contrast agent, and another patient had a perinephric hematoma develop that necessitated evacuation. There were four postoperative deaths (30-day mortality). Two of these deaths were caused by postoperative myocardial infarction. The other two patients had progressive renal failure develop that necessitated dialysis. These patients later died of the disease process despite supportive care. Follow-up renal artery duplex scan studies and angiograms were available on 96 patients (76%). The mean peak systolic renal/aortic ratio on duplex scanning was 2.2. Life-table analysis yielded a 74% primary patency rate and an 85% secondary patency rate at 36 months. This retrospective analysis showed the effectiveness of combining percutaneous transluminal angioplasty with stent deployment for significant renal artery stenosis to treat renovascular hypertension.

[B-technique after augmentation mammaplasty to correct dislocation of nipple and areola]

"B-technique" was first developed for breast reduction. In the past there were some new information characterizing the "B-technique" as being a good method for some breast cancer patients undergoing conversation surgery as well. In this paper we report on a patient suffering from anisomastia; after augmentation mammaplasty the "B-technique" was used to put the nipple and areola in the right position. If the dislocation of the nipple is not extreme we considered the "B-technique" a favourable method to obtain a good aesthetic result.

Survey on equine cryptosporidiosis in Poland and the possibility of zoonotic transmission

The present study was undertaken to investigate the prevalence of Cryptosporidium infection in horses used for recreational riding as well as in humans. A total of 106 faecal specimens from horses raised in 4 localities of western Poland and 6 stool samples from 3 persons who had constant or sporadic contact with horses were screened microscopically for oocysts using modified Ziehl-Neelsen staining. Enzyme immunoassay (EIA) was additionally used for the detection of coproantigen in human stool samples as well as in 43 randomly selected horse faecal samples. The overall infection rate of horses determined by microscopic examination was 9.4%. To our knowledge, this is the first report of cryptosporidial infection in horses in Poland. The infection was identified only in adult horses raised on 2 of 4 examined farms. The intensity of equine cryptosporidial infection was light, as a rule. None of the infected horses appeared clinically ill. The real overall infection rate in horses could be higher. Among 43 faecal specimens additionally processed by EIA, 5 samples were positive both for oocysts and coproantigen, whereas in 7 faecal samples only the parasite coproantigen was detected. The morphometric analysis of oocysts indicated that the horses were most probably infected with C. parvum. Of 3 examined persons, cryptosporidial infection was identified in a rider who had sporadic contact with horses.

Calcium-induced structural changes of cartilage proteoglycans studied by H NMR relaxometry and diffusion measurements

1H transverse nuclear magnetic relaxation times (T2) and self-diffusion coefficients (SDCs) of water were measured in isolated proteoglycan aggregates from pig articular cartilage. The influence of varying osmotic pressure, as well as of different calcium concentrations, on the samples was investigated. Due to a structural transition of the proteoglycans that results from changed electrostatic interactions at higher calcium concentrations, an additional fraction of water protons is observable. These protons are characterized by a very long T2 value and low, restricted diffusion. Additionally, electron microscopic elemental analyses and XFA investigations were performed to estimate the amount of calcium taken up by the proteoglycans. A model for the calcium-mediated structural transition of the cartilage proteoglycans is proposed that explains the experimental results. The investigations suggest the ability of proteoglycans to act as a calcium-concentrating agent and suggest their important role in the calcification process of articular cartilage.

[Cryptosporidiosis in HIV-positive patients]

Cryptosporidium parvum is a coccidian parasite that affects millions of people worldwide. Clinical outcome of human cryptosporidiosis differs between immunocompetent and immnunodeficient individuals. C. parvum is responsible for causing protracted and life-threatening diarrhea, biliary, and pulmonary infections in immunocompromised persons, especially in patients with AIDS. Though no effective treatment has been found so far, early diagnosis may be useful in controlling the infection. Thirty-eight stool specimens obtained from 35 HIV-positive patients admitted to the Clinic of Infectious Diseases in Poznań, Poland, were examined for the detection of oocysts, coproantigen and DNA of Cryptosporidium using standard microscopic, immunologic and molecular diagnostic methods. The presence of Cryptosporidium was detected in 10 HIV-positive patients. Oocysts, coproantigen and DNA of this parasite were identified solely in one specimen while Cryptosporidium DNA was detected in 8 specimens. Cryptosporidium coproantigen was found only in one sample. Although, the PCR was the most useful technique in the detection of Cryptosporidium in HIV-positive patients it should be noted that PCR has many pitfalls and needs to be carefully controlled to avoid both false positive and false negative results.

Na+-dependent phosphate cotransporters: the NaPi protein families

In vertebrates, the level of inorganic phosphate (Pi) is tightly balanced both inside the cell and in the whole organism. A number of different Na+-dependent Pi cotransport systems involved in Pi homeostasis have been identified and characterized at the molecular level in the past 7 years. The transporters constitute three different protein families denoted NaPi-I, NaPi-II and NaPi-III. NaPi-I from the rabbit was the first member of this family to be cloned. However, it still resists efforts to unravel its physiological role and a clear-cut functional identity: is it a Cl-channel, a Na+/Pi cotransporter, a regulator, or does it perform a combination of these functions? These questions provide a slight taste of the problems associated with orphan genes derived from sequencing projects. The members of the NaPi-II protein family are crucially involved in tightly controlled renal Pi excretion and, as recently discovered, intestinal Pi absorption. The expression and the cellular distribution of NaPi-II in the proximal tubular epithelium are affected by hormonal and metabolic factors known to influence extracellular fluid Pi homeostasis. Recently, the expression of NaPi-II has been demonstrated in osteoclasts and brain;however, the physiological roles of NaPi-II in these tissues remain to be established. The members of the third protein family, NaPi-III, have been identified on the basis of their function as viral receptors. The widespread expression of this family suggests that NaPi-III is involved in supplying the basic cellular metabolic needs for Pi.

Structural integrity of resin-modified glass ionomers as affected by the delay or omission of light activation

Since light activation of resin-modified glass ionomers as a means of polymerizing the HEMA is usually done shortly after mixing occurs, the acid-base reaction will proceed mainly within a formed HEMA-polymer matrix. Delaying or omitting light activation may alter the structure and consequently its integrity. The aim of this study was to investigate the effect on the structural integrity of Fuji II LC, Photac-Fil, and Vitremer by delaying or omitting light initiation as compared with the integrity when light activation is performed 2 min after mixing occurs. We evaluated integrity by three-body wear experiments, conducted 8 hrs after sample preparation, to establish the integrity in the early phase of hardening, as well as after 1 wk and after 4 mos, to follow the materials throughout the process of maturation. When light activation was delayed for 1 hr, the structural integrity of Fuji II LC and Photac-Fil improved significantly in the early stages of hardening. In the case of Vitremer, an hour's delay of light activation significantly decreased integrity, which declined further when light activation was omitted. Fuji II LC was not affected by the omission of light activation, while Photac-Fil was markedly weakened. After 4 mos of aging, most of the samples of each product which had been cured by the different methods attained equal integrity, with the exception of the non-light-activated Vitremer samples, which remained weaker. We concluded that the structural integrity of resin-modified glass-ionomer cements benefits from a chemical integration of the polyalkenoate and poly-HEMA networks, as in Vitremer. Improvement in the structural integrity in the early phase for cements with a mechanical entanglement of the matrices, as in Fuji II LC and Photac-Fil, requires an acid-base reaction, a considerable portion of which may take place before activation of the HEMA polymerization.

Immune surveillance in the injured nervous system: T-lymphocytes invade the axotomized mouse facial motor nucleus and aggregate around sites of neuronal degeneration

Although the CNS is an established immune-privileged site, it is under surveillance by the immune system, particularly under pathological conditions. In the current study we examined the lymphocyte infiltration, a key component of this neuroimmune surveillance, into the axotomized facial motor nucleus and analyzed the changes in proinflammatory cytokines and the blood-brain barrier. Peripheral nerve transection led to a rapid influx of CD3-, CD11a (alphaL, LFA1alpha)- and CD44-immunoreactive T-cells into the axotomized mouse facial motor nucleus, with a first, low-level plateau 2-4 d after injury, and a second, much stronger increase at 14 d. These T-cells frequently formed aggregates and exhibited typical cleaved lymphocyte nuclei at the EM level. Immunohistochemical colocalization with thrombospondin (TSP), a marker for phagocytotic microglia, revealed aggregation of the T-cells around microglia removing neuronal debris. The massive influx of lymphocytes at day 14 was also accompanied by the synthesis of mRNA encoding IL1beta, TNFalpha, and IFN-gamma. There was no infiltration by the neutrophil granulocytes, and the intravenous injection of horseradish peroxidase also showed an intact blood-brain barrier. However, mice with severe combined immunodeficiency (SCID), which lack differentiated T- and B-cells, still exhibited infiltration with CD11a-positive cells. These CD11a-positive cells also aggregated around phagocytotic microglial nodules. In summary, there is a site-selective infiltration of activated T-cells into the mouse CNS during the retrograde reaction to axotomy. The striking aggregation of these lymphocytes around neuronal debris and phagocytotic microglia suggests an important role for the immune surveillance during neuronal cell death in the injured nervous system.

Chloride conductance and Pi transport are separate functions induced by the expression of NaPi-1 in Xenopus oocytes

Expression of the protein NaPi-1 in Xenopus oocytes has previously been shown to induce an outwardly rectifying Cl- conductance (GCl), organic anion transport and Na+-dependent Pi-uptake. In the present study we investigated the relation between the NaPi-1 induced GCl and Pi-induced currents and transport. NaPi-1 expression induced Pi-transport, which was not different at 1-20 ng/oocyte NaPi-1 cRNA injection and was already maximal at 1-2 days after cRNA injection. In contrast, GCl was augmented at increased amounts of cRNA injection (1-20 ng/oocyte) and over a five day expression period. Subsequently all experiments were performed on oocytes injected with 20 ng/oocytes cRNA. Pi-induced currents (Ip) could be observed in NaPi-1 expressing oocytes at high concentrations of Pi (>/= 1 mm Pi). The amplitudes of Ip correlated well with GCl. Ip was blocked by the Cl- channel blocker NPPB, partially Na+-dependent and completely abolished in Cl- free solution. In contrast, Pi-transport in NaPi-1 expressing oocytes was not NPPB sensitive, stronger depending on extracellular Na+ and weakly affected by Cl- substitution. Endogenous Pi-uptake in water-injected oocytes amounted in all experiments to 30-50% of the Na+-dependent Pi-transport observed in NaPi-1 expressing oocytes. The properties of the endogenous Pi-uptake system (Km for Pi > 1 mM; partial Na+- and Cl--dependence; lack of NPPB block) were similar to the NaPi-1 induced Pi-uptake, but no Ip could be recorded at Pi-concentrations </=3 mM. In summary, the present data suggest that Ip does not reflect charge transfer related to Pi-uptake, but a Pi-mediated modulation of GCl.

Regulation of MCSF receptors on microglia in the normal and injured mouse central nervous system: a quantitative immunofluorescence study using confocal laser microscopy

The macrophage colony-stimulating factor (MCSF) is a 40-76-kD glycoprotein that plays an important role in the activation and proliferation of microglia both in vitro and in injured neural tissue. Here, we examined the regulation of MCSF receptor (MCSFR) and MCSF in the normal and injured mouse central nervous system (CNS) by using confocal laser microscopy, quantitative immunofluorescence, and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. Immunohistochemistry on fixed, floating tissue sections demonstrated low to moderate MCSFR immunoreactivity (MCSFR-IR) on microglia in the gray and white matter throughout the mouse CNS in the forebrain, brainstem, cerebellum, and spinal cord. High levels of MCSFR-IR were restricted to the superficial layer of the spinal cord dorsal horn, substantia nigra, and area postrema, a CNS region that lacks the blood-brain barrier. CNS injury led to a strong and specific increase in MCSFR-IR in the directly injured dorsal forebrain, in the cervical spinal cord (C2) after transection of the sensory, minor occipital nerve, and in the axotomized facial motor nucleus. Further investigation at the mRNA level in the facial nucleus model showed that this increase was accompanied by a rapid induction of the transcript for MCSFR, with a peak 1-2 days after injury, but only a constitutive expression of MCSF-mRNA. In summary, although normal levels of MCSF receptor in most microglia are low, microglial activation is accompanied by a rapid and massive increase. In view of the constitutive expression of MCSF, the early upregulation of the MCSF receptor may play a central role in preparing these macrophage-related cells to take part in the cellular response to CNS injury.

Increased serum and mRNA levels of RANTES associated with elevated levels of activated CD8+CD38+ T cells in HIV-1 infected individuals

The serum levels of the beta-chemokine RANTES and, albeit less, MIP-1 beta were found to be increased in 37 HIV-1 infected compared to seronegative individuals. In contrast the serum levels of IL-16 were only sporadically elevated in seropositives as well as in seronegatives. Concomitantly, the RANTES gene expression increased about tenfold in seropositives, whereas the MIP-1 beta and IL-16 mRNA levels were not elevated. No correlation between the increase of the MIP-1 beta and RANTES serum concentrations and the plasma virus load, the number of the peripheral CD4+ T cells or the therapy status of the patients was found. However, the increased proportion of activated CD8+CD38+ T cells in the peripheral blood of all seropositives paralleled the increased RANTES serum levels detected indicating that immune activation in HIV-1-infected individuals may contribute to increased RANTES serum levels.

Translated anti-sense product of the Na/phosphate co-transporter (NaPi-II)

The homeostasis of Pi in marine teleosts is maintained by renal Pi secretion as well as by Pi reabsorption. A Na/Pi co-transport system belonging to the NaPi-II protein family is instrumental in tightly controlled renal Pi handling in mammals and fish. We have isolated an NaPi-II related cDNA from winter flounder. It was cloned from a female gonad cDNA library and is 624 bp long. The transcript is expressed in female and male flounder gonads as well as in kidney and intestine, although at very low levels. RNase H digestion experiments revealed an opposite orientation of the transcript with regard to NaPi-II-related mRNA. The anti-sense orientation was confirmed by genomic sequence analysis and Southern blotting. Alluding to the sense transcript, the anti-sense transcript was denoted IPAN. The open reading frame of IPAN encodes a basic protein of 68 amino acid residues. Immunohistochemistry confined the anti-sense related protein, Ipan, to a submembranous compartment of immature oocytes, suggesting a role in oocyte development. In kidney and intestine Ipan is partly co-localized with the Na/Pi co-transporter, implying a regulatory function for the anti-sense protein. However, direct protein-protein interaction could not be established. The existence of a putative open reading frame in other species extends the biological significance of the novel protein.

The Na+-phosphate cotransport system (NaPi-II) with a cleaved protein backbone: implications on function and membrane insertion

1. Renal handling of inorganic phosphate (Pi) involves a Na+-Pi cotransport system which is well conserved between vertebrates. The members of this protein family, denoted NaPi-II, share a topology with, it is thought, eight transmembrane domains. The transporter is proposed to be proteolytically cleaved within a large hydrophilic loop in vivo. 2. The consequences of an interrupted backbone were tested by constructing cDNA clones encoding different N- (1-3 and 1-5) and C-terminal (4-8 and 6-8) complementary fragments of NaPi-II from winter flounder. When the cognate fragments were used in combination (1-3 plus 4-8; 1-5 plus 6-8) they comprised the full complement of the putative transporter domains. 3. None of the four individual fragments or the 1-5 plus 6-8 combination when expressed in Xenopus oocytes increased Pi flux. Coexpression of fragments 1-3 plus 4-8 stimulated transport activity identical to that for expressed wild-type NaPi-II with regard to pH dependency and Km for Na+ and Pi binding; however, the maximal transport rate (vmax) was lower. 4. Immunohistochemistry on cryosections confined the functionally active 1-3 plus 4-8 combination to the oocyte membrane. This was not the case for the 1-5 plus 6-8 combination or any of the individual fragments, all of which failed to induce fluorescence. 5. A second immunohistochemical approach using intact oocytes allowed determination of the extracellular regions of the protein. Epitopes within the loop between transmembrane domains 3 and 4 enhanced fluorescence. Neither N- nor C-terminal tags induced fluorescence.