A Mechanistic Systems Pharmacology Model for Prediction of LDL Cholesterol Lowering by PCSK9 Antagonism in Human Dyslipidemic Populations

PCSK9 is a promising target for the treatment of hyperlipidemia and cardiovascular disease. A Quantitative Systems Pharmacology model of the mechanisms of action of statin and anti-PCSK9 therapies was developed to predict low density lipoprotein (LDL) changes in response to anti-PCSK9 mAb for different treatment protocols and patient subpopulations. Mechanistic interactions and cross-regulation of LDL, LDL receptor, and PCSK9 were modeled, and numerous virtual subjects were developed and validated against clinical data. Simulations predict a slightly greater maximum percent reduction in LDL cholesterol (LDLc) when anti-PCSK9 is administered on statin background therapy compared to as a monotherapy. The difference results primarily from higher PCSK9 levels in patients on statin background. However, higher PCSK9 levels are also predicted to increase clearance of anti-PCSK9, resulting in a faster rebound of LDLc. Simulations of subjects with impaired LDL receptor (LDLR) function predict compromised anti-PCSK9 responses in patients such as homozygous familial hypercholesterolemics, whose functional LDLR is below 10% of normal.

Characterization of the association of connexins and ZO-1 in the lens

ZO-1 (Zona Occludens protein 1) has previously been shown to bind Cx43alpha1. This interaction involves the most C-terminal residues of Cx43alpha1 and the second PDZ-domain of ZO-1. The biological significance of this interaction is not well understood. The similarity of the C-terminal residues of the lens connexins Cx46alpha3 and Cx50alpha8 to Cx43alpha1 prompted us to examine if ZO-1 is expressed in the lens, and if ZO-1 interacts with lens connexins. A high level of ZO-1 expression was detected in the mouse lens. Lens connexins were shown to co-immunoprecipitate with ZO-1, and the interaction was found to involve similar domains as those previously demonstrated for the Cx43alpha1/ZO-1 interaction (Nielsen et al. manuscript in preparation). Futhermore, transient expression of Cx46alpha3 and Cx50alpha8 in cell culture showed colocalization of gap junction plaques with ZO-1, further suggesting that lens connexins interact with ZO-1. Sequence comparison suggests that a large number of connexins of the alpha subclass may interact with ZO-1. Using the lens as a system to study connexin/ZO-1 interactions may further our understanding of their biological significance in the lens, as well as in other organs.

Defining a link between gap junction communication, proteolysis, and cataract formation

Disruption of the connexin alpha 3 (Cx46) gene (alpha 3 (-/-)) in mice results in severe cataracts within the nuclear portion of the lens. These cataracts are associated with proteolytic processing of the abundant lens protein gamma-crystallin, leading to its aggregation and subsequent opacification of the lens. The general cysteine protease inhibitor, E-64, blocked cataract formation and gamma-crystallin cleavage in alpha 3 (-/-) lenses. Using a new class of activity-based cysteine protease affinity probes, we identified the calcium-dependent proteases, m-calpain and Lp82, as the primary targets of E-64 in the lens. Profiling changes in protease activities throughout cataractogenesis indicated that Lp82 activity was dramatically increased in alpha 3 (-/-) lenses and correlated both spatially and temporally with cataract formation. Increased Lp82 activity was due to calcium accumulation as a result of increased influx and decreased outflux of calcium ions in alpha 3 (-/-) lenses. These data establish a role for alpha 3 gap junctions in maintaining calcium homeostasis that in turn is required to control activity of the calcium-dependent cysteine protease Lp82, shown here to be a key initiator of the process of cataractogenesis.

Effects of mental stress on brachial artery flow-mediated vasodilation in healthy normal individuals

BACKGROUND

Mental stress is associated with increased risk for cardiovascular events, possibly because of acute increases in endogenous catecholamines. Recently, brachial artery flow-mediated vasodilation has been used for noninvasive assessment of macrovascular endothelial function. The effect of mental stress and its associated changes in sympathetic activation on brachial artery endothelium-dependent vasomotor tone in vivo remains unknown.

METHODS AND RESULTS

Two-dimensional ultrasound was used to measure brachial artery flow-mediated vasodilation before and after mental stress (provoked by a standard arithmetic challenge) in 21 healthy individuals (10 men, 11 women; average age 23.5 years). The flow stimulus resulted from a 3-minute cuff occlusion of distal forearm blood flow, causing distal hyperemia and a transient 2- to 3-fold increase in brachial artery blood flow on cuff release. During mental stress, heart rate increased on average by 29.6% and blood pressure increased on average by 17.9%. The sympathetic stimulus resulted in a 64% average increase in flow-mediated vasodilator response (P <.001). The enhanced vasodilator response during mental stress was similar for men and women.

CONCLUSIONS

Mental stress can have marked effects on endothelium-dependent, flow-mediated vasodilation in healthy, normal individuals. Similar studies in individuals with impaired endothelial function may further our understanding of the role of mental stress in the development of cardiovascular events.

MUC1 isoform specific monoclonal antibody 6E6/2 detects preferential expression of the novel MUC1/Y protein in breast and ovarian cancer

The products of the MUC1 gene are known to be highly expressed in human breast cancer cells. The best characterized MUC1 protein is a polymorphic, type 1 transmembrane molecule containing a large extracellular domain composed primarily of a variable number of 20 amino acid tandem repeats. We have recently identified a novel protein product of the MUC1 gene, the MUC1/Y protein, that is also a transmembrane protein but is devoid of the tandem repeat array and its immediate flanking sequences. To analyze its expression in tumor cells we generated monoclonal antibodies directed against the MUC1/Y extracellular domain (anti-MUC1/Yex MAbs). Epitope mapping identified the MAb, 6E6, which recognized the MUC1/Y isoform with exquisite specificity- the repeat-array-containing MUC1 isoform could not compete out this immunoreactivity. A 30mer peptide which is unique for MUC1/Y and corresponds to the "join" region generated by the MUC1/Y specific splice, abrogated all 6E6 MAb immunoreactivity towards MUC1/Y. Immunoprecipitation of the MUC1/Y protein with 6E6 MAbs revealed that, in contrast with the proteolytic cleavage of the tandem-repeat-array-containing MUC1 isoform, MUC1/Y is not cleaved. Flow cytometry analyses using the 6E6 MAbs demonstrated that the MUC1/Y isoform is expressed on the cell surface of both MCF-7 breast cancer cells and malignant epithelial cells present in effusions obtained from breast and ovarian cancer patients. Our results unequivocally establish that the MUC1/Y protein is expressed on the surface of breast cancer cells and cells of other epithelial malignancies. The anti-MUC1/Y MAbs described here can target MUC1/Y expressing tumor cells in vivo and are likely to be important reagents both for epithelial tumor diagnosis and immunotherapy.

The breast cancer-associated MUC1 gene generates both a receptor and its cognate binding protein

MUC1 proteins, some of which contain a mucin-like domain and others lacking this region, can be generated from the human breast cancer-associated MUC1 gene by alternative splicing. The MUC1/Y isoform is devoid of the mucin domain and is a cell membrane protein that undergoes transphosphorylation on both serine and tyrosine residues. We have identified cognate binding proteins that specifically interact with the extracellular domain of MUC1/Y. Coimmunoprecipitation analyses clearly revealed the presence of complexes composed of MUC1/Y and its cognate binding proteins in primary breast tumor tissue. MUC1/Y-expressing mammary tumor cells can be specifically targeted, in vivo, with the labeled cognate binding protein. The k(D) of MUC1/Y for its binding proteins was estimated as 1.2 nM. The MUC1/Y binding proteins are also derived from the MUC1 gene and represent the secreted mucin-like polymorphic MUC1 proteins MUC1/SEC and MUC1/REP, which contain a tandem repeat array. Whereas nonposttranslationally modified MUC1/Y bound efficiently to MUC1/SEC, the latter mucin-like protein had to be posttranslationally modified in a cell-type specific manner to bind MUC1/Y. The interaction of MUC1/Y with MUC1/SEC has important biological functional correlates: (a) it induces MUC1/Y phosphorylation; and (b) it has a pronounced effect on cell morphology. These findings suggest that MUC1/Y and MUC1/SEC form an active receptor/ cognate binding protein complex that can elicit cellular responses. The proteins comprising this complex are, thus, generated by alternative splicing from one and the same gene, namely the MUC1 gene.

A pharmacokinetic study of intravenous itraconazole followed by oral administration of itraconazole capsules in patients with advanced human immunodeficiency virus infection

A randomized, open-label, comparative study was conducted in 30 male patients with moderately advanced human immunodeficiency virus (HIV) infection to examine the pharmacokinetics of an investigational intravenous preparation of itraconazole compared with pharmacokinetics after administration of itraconazole capsules. The study also assessed whether adequate plasma concentrations of itraconazole could be rapidly achieved with the intravenous formulation and then maintained after cessation of intravenous therapy with itraconazole capsules. All patients received 200 mg intravenous itraconazole as a 1-hour infusion in 40% hydroxypropyl-beta-cyclodextrin (HP-beta-CD) vehicle twice daily for 2 days, and then 200 mg intravenously once daily for 5 days. Patients then received itraconazole capsules, either 200 mg twice daily or 200 mg once daily for 28 days. Steady-state plasma concentrations of itraconazole were reached by day 3 with intravenous infusion, a much shorter time than observed with administration of itraconazole capsules. Steady-state concentrations of itraconazole and hydroxyitraconazole were effectively maintained during the rest of the intravenous infusions of itraconazole. Oral follow-up with administration of 200-mg capsules once daily could not maintain the plasma concentrations of itraconazole and hydroxyitraconazole obtained at the end of the intravenous treatment, whereas twice-daily oral administration maintained or increased these concentrations. Mean plasma concentrations of itraconazole and hydroxyitraconazole on day 7 were similar to those on day 36 in the twice-daily group. Mean renal clearance was comparable to mean total body clearance, and approximately 93% to 101% of the HP-beta-CD was excreted unchanged in urine within 12 hours of administration. The HP-beta-CD was essentially eliminated through the kidney, and little accumulation in the body was observed in this patient population. Adverse events during the intravenous phase were most commonly associated with intravenous administration. Intravenous infusion of itraconazole for 7 days followed by administration of itraconazole capsules twice daily for 28 days is an effective dose regimen in patients with advanced HIV infection.

Insulin and prolactin synergize to induce translation of human serum albumin in the mammary gland of transgenic mice

A dramatic uncoupling of the expression of chimaeric beta-lactoglobulin (BLG)/human serum albumin (HSA) gene constructs at the RNA and protein levels was observed in cultured mammary explants of virgin transgenic mice. Upon explantation, both HSA RNA and protein were expressed at high levels. However, when the explants were grown in hormone-free medium. HSA RNA continued to accumulate, whereas the synthesis of the corresponding protein was dependent on the presence of insulin and prolactin with a minor contribution of hydrocortisone. The untranslated HSA RNA was indistinguishable from its translatable counterpart in its mobility on agarose gels, was transported normally from the nucleus to the cytoplasm and was translated efficiently in rabbit reticulocyte lysate. In the presence of cycloheximide, HSA RNA rapidly disappeared suggesting a dependency on ongoing protein synthesis. Its estimated half-life of 5-6 h in hormone-free medium increased significantly in the presence of insulin, hydrocortisone and prolactin and was comparable to that of beta-casein RNA. The uncoupling of the expression of the BLG/HSA transgenes at the RNA and protein levels was also confirmed by in situ hybridization and immunohystochemistry on sections from virgin mammary explants. HSA synthesis was initiated within 13 h of the addition of insulin and prolactin in explants that had accumulated untranslated HSA RNA and was fourfold higher than that observed with insulin alone. Addition of hydrocortisone contributed to an additional 20% in HSA synthesis. We believe this is the first demonstration of translational control of exogenous milk protein gene expression in the mammary gland of transgenic animals.

Preferential expression of novel MUC1 tumor antigen isoforms in human epithelial tumors and their tumor-potentiating function

The human MUC1 gene expresses at least 2 type 1 membrane proteins: MUC1/REP, a polymorphic high m.w. MUC1 glycoprotein often highly expressed in breast cancer tissues and containing a variable number of tandem 20 amino acid repeat units, and the MUC1/Y protein, which lacks this repeat array and, therefore, is not polymorphic. Despite their documented importance in signal transduction processes, the relative expression of the 2 isoforms in epithelial tumors is unknown. Using antibody reagents which recognize different MUC1 domains, the expression of these isoforms in malignant epithelial cells has been evaluated. A comparison of the amounts of the 2 isoforms revealed preferential expression of the novel MUC1/Y protein in breast cancer tissue samples. Furthermore, although the MUC1/REP protein is almost undetectable in HeLa cervical adenocarcinoma epithelial cells, the MUC1/Y isoform is extensively expressed in these cells. The presence of the MUC1/Y sequence as well as that of an additional tandem-repeat-array-lacking isoform, designated MUC1/X, were demonstrated by reverse transcriptase PCR amplification of RNA extracted from HeLa and ovarian carcinoma cells. It has been shown previously that the MUC1 cytoplasmic domain interacts with the SH2 domain containing GRB2 protein, which transduces signals to ras, a protein which in its activated form can lead to cell transformation. We present here data demonstrating that MUC1/Y isoform expression increases the tumorigenic potential of DA3 mouse mammary epithelial cells; in contrast, potentiation of tumorigenicity is not observed with MUC1/REP expression. Our studies thus demonstrate that expression of the MUC1 gene in epithelial tumors can give rise to substantial levels of MUC1 proteins devoid of the tandem repeat array, which are generated by alternative splicing mechanisms.

Detection of a secreted MUC1/SEC protein by MUC1 isoform specific monoclonal antibodies

Although MUC1 proteins are known to be secreted by breast cancer cells, the mechanism of their release from the cell is still obscure. Our previously reported MUC1 cDNA sequences suggested the existence of a secreted MUC1 isoform, MUC1/SEC, that includes a sequence of intron 2, and terminates prematurely at a stop codon within this intron. It is thus devoid of a transmembrane domain. As no formal evidence for MUC1/SEC expression at the protein level had been provided, we generated monoclonal antibodies (mAbs) against a peptide sequence (sec peptide) that is unique for the MUC1/SEC protein. Two anti-sec peptide mAbs were obtained which reacted strongly with (a) the immunizing peptide, (b) recombinant MUC1/SEC protein, and (c) MUC1 proteins secreted from breast cancer cells. The immunoreactivity of the anti-sec peptide mAbs with MUC1 proteins secreted by breast cancer cells was specifically inhibited by the sec peptide-it was completely unaffected by a peptide sequence that represents a MUC1 repeat motif. Significantly, the anti-sec peptide mAbs also detected MUC1/SEC protein in sera of breast cancer patients. We have established here that these mAbs recognize the MUC1/SEC isoform via a peptide sequence which is unique for the MUC1/SEC protein. Our studies thus demonstrate that the MUC1/SEC protein is a bona-fide MUC1 isoform and that its expression may contribute to the secretion of MUC1 proteins by secretory epithelial cells in general and breast cancer cells in particular.

Treatment of human immunodeficiency virus infection with saquinavir, zidovudine, and zalcitabine. AIDS Clinical Trials Group

BACKGROUND

In patients with human immunodeficiency virus (HIV) infection, combined treatment with several agents may increase the effectiveness of antiviral therapy. We studied the safety and efficacy of saquinavir, an HIV-protease inhibitor, given with one or two nucleoside antiretroviral agents, as compared with the safety and efficacy of a combination of two nucleosides alone.

METHODS

In this double-blind trial, patients with HIV infection were randomly assigned to receive either saquinavir (1800 mg per day) plus both zidovudine (600 mg per day) and zalcitabine (2.25 mg per day) or zidovudine plus either saquinavir or zalcitabine. The 302 patients enrolled had CD4+ counts of 50 to 300 cells per cubic millimeter and had previously received zidovudine for a median of 27 months. The study lasted 24 weeks, with an optional double-blind extension period of an additional 12 to 32 weeks.

RESULTS

Ninety-six percent of the patients completed the 24-week study. In all three treatment groups, CD4+ cell counts rose at first and then fell gradually. The normalized area under the curve for the CD4+ count was greater with the three-drug combination than with either saquinavir and zidovudine (P=0.017) or zalcitabine and zidovudine (P<0.001). There were significantly greater reductions in plasma HIV with the three-drug combination than with the other regimens when peripheral-blood mononuclear cells were cultured for HIV and HIV RNA was assessed, and there were greater decreases in serum neopterin and beta2-microglobulin levels. There were no major differences in toxic effects among the three treatments.

CONCLUSIONS

Treatment with saquinavir, zalcitabine, and zidovudine was well tolerated. This drug combination reduced HIV-1 replication, increased CD4+ cell counts, and decreased levels of activation markers in serum more than did treatment with zidovudine and either saquinavir or zalcitabine. Studies are warranted to evaluate whether the three-drug combination will reduce morbidity and mortality.

Preoperative diagnosis of thyroid papillary carcinoma by reverse transcriptase polymerase chain reaction of the MUC1 gene

As thyroid nodules are common, it is imperative to recommend operation only to those with a high risk of malignancy. Fine-needle aspiration (FNA) biopsy, which is widely used for this purpose, is limited by the considerable rate of non-diagnostic or non-interpretable conclusions. Therefore, it is highly desirable to acquire a new diagnostic means for thyroid cancer. We have recently described a marked over-expression of the MUC1 gene in thyroid papillary-carcinoma tissue, as compared with various benign thyroid pathologies. As the amount of mRNA obtainable by FNA is not amenable to hybridization analysis, we amplified the mRNA sequence of the MUC1-gene upstream of the variable number tandem repeat array using the reverse-transcription polymerase chain reaction (RT-PCR). Seven out of 8 FNA samples obtained from thyroid papillary carcinoma resulted in 336 and 309 base-pair products. In contrast, in all 13 FNA samples obtained from various benign pathologies, only the smaller RT-PCR product was observed. Sequence analysis of the RT-PCR products indicates that alternative splicing of the exon 2 acceptor site accounts for the difference between the 2 amplification products. It is suggested that RT-PCR of the MUC1-gene transcript may add a biomolecular diagnostic dimension to the routine cytological preoperative FNA diagnosis.

Combination therapy with zidovudine, didanosine and saquinavir

The goal of AIDS Clinical Trials Group (ACTG) Protocol 229 was to evaluate the shorter term (24 week) and longer term (48 week) safety and activity of the HIV-1 proteinase inhibitor saquinavir in combination with zalcitabine (ddC) and zidovudine (ZDV) versus saquinavir in combination with ZDV versus ddC in combination with ZDV. This study confirms and extends the conclusions from the first 24 weeks of this study and showed that in subjects with extensive prior antiretroviral experience, the triple combination of saquinavir, ddC and ZDV was well-tolerated, safe and remained superior to the other double drug regimens as measured by CD4+ cell counts, quantitative HIV-1 microculture and plasma HIV-1 RNA levels.

Developmental regulation of the ovine beta-lactoglobulin/human serum albumin transgene is distinct from that of the beta-lactoglobulin and the endogenous beta-casein genes in the mammary gland of transgenic mice

We compared the developmental pattern of expression of the sheep beta-lactoglobulin (BLG), the chimeric BLG/human serum albumin (HSA), and the endogenous murine beta-casein genes in the mammary gland of virgin, pregnant and lactating transgenic mice, both at the RNA (expression) and protein (synthesis and secretion) levels. The BLG and casein genes were expressed at very low levels in virgin animals and during early stages of pregnancy. The increase in the expression of these genes started at the second half of pregnancy and reached a peak between the end of pregnancy and day 10 of lactation. The accumulation of their RNA coincided with that of the corresponding proteins, indicating a transcriptional control of expression of these genes. The expression and secretion patterns of the endogenous casein gene in transgenic and nontransgenic mice were indistinguishable. The hybrid BLG/HSA gene constructs displayed distinct patterns of expression in virgin animals and at early stage of pregnancy, from that of the BLG transgene or the endogenous mouse milk protein gene. High levels of expression (17-60% of that on day 18 of pregnancy) were detected in the mammary gland of virgin animals. At day 5 of pregnancy there was a dramatic decrease in HSA synthesis and secretion in all transgenic strains tested. The down-regulation, revealed by immunoprecipitation and immunohistochemical studies, demonstrated that at that stage of pregnancy only 10-18% of ductal structures contained HSA expressing cells in contrast to the majority of ducts expressing HSA in virgin animals. These morphological studies also demonstrated that the down-regulation in HSA synthesis and secretion was correlated with the transition from ducts comprised of a single layer of epithelial cells (characteristic of the virgin state) to ducts composed of multilayers of such cells. In two of the three transgenic strains tested, the down-regulation at the protein level was associated with a similar decrease in HSA transcripts. In the exceptional strain no. 23, HSA transcripts continued accumulating even at this stage. The differences in the control of expression at the RNA level between these transgenic strains were also confirmed by in situ hybridization. Our results suggest the involvement of at least two regulatory mechanisms effective at early stages of gestation in the control of expression/secretion of the HSA transgene targeted for expression in the mammary gland by the BLG milk protein promoter. These putative mechanisms may play key roles in the interplay between normal mammogenesis and lactogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Tyrosine phosphorylation of the MUC1 breast cancer membrane proteins. Cytokine receptor-like molecules

Phosphorylation on tyrosine residues is a key step in signal transduction pathways mediated by membrane proteins. Although it is known that human breast cancer tissue expresses at least 2 MUC1 type 1 membrane proteins (a polymorphic high molecular weight MUC1 glycoprotein that contains a variable number of tandem 20 amino acid repeat units, and the MUC1/Y protein that is not polymorphic and is lacking this repeat array) their function in the development of human breast cancer has remained elusive. Here it is shown that these MUC1 proteins are extensively phosphorylated, that phosphorylation occurs primarily on tyrosine residues and that following phosphorylation the MUC1 proteins may potentially interact with SH2 domain-containing proteins and thereby initiate a signal transduction cascade. As with cytokine receptors, the MUC1 proteins do not harbor intrinsic tyrosine kinase activity yet are tyrosine phosphorylated and the MUC1/Y protein participates in a cell surface heteromeric complex whose formation is mediated by two cytoplasmically located MUC1 cysteine residues. Furthermore, the MUC1/Y protein demonstrates sequence similarity with sequences present in cytokine receptors that are known to be involved in ligand binding. Our results demonstrate that the two MUC1 isoforms are both likely to function in signal transduction pathways and to be intimately linked to the oncogenetic process and suggest that the MUC1/Y protein may act in a similar fashion to cytokine receptors.

Characterization and molecular cloning of a novel MUC1 protein, devoid of tandem repeats, expressed in human breast cancer tissue

The human breast cancer marker protein, MUC1, is a polymorphic transmembrane molecule containing a large extracellular domain that is primarily composed of a variable number of highly conserved 20-amino-acid tandem repeats. We report here the detection of a novel invariantly sized 1.2-kb MUC1 mRNA, in addition to the large polymorphic mRNAs, by probing Northern blots with MUC1-cDNA-unique-sequence probes. The nucleotide sequence of this novel MUC1 mRNA demonstrates that it is identical to the MUC1 cDNA sequences downstream and upstream to the tandem-repeat array of the transmembrane form of MUC1. However, it contains neither the central tandem repeat array itself nor its directly flanking sequences that are deleted by a differential splicing event utilizing splice acceptor and donor sequences 5' and 3' to the tandem-repeat array. The splice event retains, downstream to the splice acceptor site, an open reading frame identical to that of the repeat-array-containing MUC1 thereby generating the novel MUC1/Y protein. Cells transiently transfected with the novel MUC1/Y cDNA express the MUC1/Y protein that is modified by glycosylation. The MUC1/Y protein is also readily detected in human breast cancer cells grown in vitro. Furthermore, primary breast cancer tissue samples demonstrate significant levels of the MUC1/Y protein whereas expression in tissue adjacent to the tumor is undetectable. Molecular characterization presented here, of the novel MUC1/Y molecule lacking the repeat array, suggests that it is likely to play a role distinct to that of the polymorphic repeat-array-positive MUC1 protein and that it may act as a new marker protein for human breast cancer.

Does a novel form of the breast cancer marker protein, MUC1, act as a receptor molecule that modulates signal transduction?

Molecular analysis of a protein highly expressed in human breast cancer, indicates the presence of a polymorphic tandem repeat domain that encodes a conserved 20 amino acid repeat motif rich in serine and threonine residues that in the mature protein, designated MUC1, are linked via O-glycosidic linkages to sugar residues. Recent studies performed in our laboratory have led to the molecular characterization of a novel MUC1 repeat array minus mRNA, generated by an alternative splicing event that deletes the central tandem repeat array and its flanking sequences. The conceptually derived amino acid sequence of the novel MUC1 protein shows that it is identical with the previously reported transmembrane MUC1 amino acid sequence except for the deletion of the central 20 amino acid tandem repeat array and sequences immediately flanking the repeat array. This indicates that the novel MUC1 protein, which is devoid of the "hallmark" feature of mucins, the tandem repeat array, may be functionally different to the much larger, heavily glycosylated polymorphic repeat array containing MUC1 proteins, that affect cell-cell interactions. Based on an analysis of its peptide sequence, we propose the hypothesis that the novel MUC1 protein may act as a receptor molecule that modulates signal transduction. Preliminary experimental data supports this hypothesis. It appears, therefore, that the MUC1 gene is multifunctional with regard to its protein products- the repeat array containing MUC1 proteins may alter cellular adhesion processes whereas the novel MUC1 protein could be acting as a receptor-like molecule participating in signal transmission.

Synthesis and secretion of human serum albumin by mammary gland explants of virgin and lactating transgenic mice

Transgenic mice were produced, carrying hybrid genes comprised of the ovine beta-lactoglobulin (BLG) milk protein gene promoter and human serum albumin (HSA) coding sequences. In situ hybridization revealed high levels of BLG/HSA hybrid mRNA, confined to the epithelial cells of the lactating mammary gland with a several hundred fold lower concentration in virgin mammary glands. During the first 24 h in culture, exceptionally high levels of HSA were secreted from explants of virgin mice, independent of hormonal control. HSA secretion was reduced considerably during subsequent days in culture and became dependent on the presence of insulin, hydrocortisone and prolactin. This temporal and hormonal pattern of regulation of HSA was different than that found for the secretion of caseins. In contrast to the vast difference in the mRNA content, the amount of HSA secreted from explants derived from lactating mice during the first 24 h in culture was only 2- to 5-fold higher than that found with explants from virgin transgenic mice, suggesting post-transcriptional control of HSA synthesis. The high-level synthesis and secretion of HSA in mammary explants of lactating mice was also dependent on the presence of insulin, hydrocortisone and prolactin. This study confirms previous suggestion that mammary explants from virgin transgenics may serve as a powerful tool for screening the potential of transgenic animals to secrete foreign proteins in their milk.

Simple bone cyst of the metacarpal

Simple bone cyst is a benign tumor-like lesion that occurs principally in the humerus and the femur. Occurrence within the hand is rare and involvement of the metacarpals is even more uncommon. Two similar cases of a simple bone cyst affecting the metacarpals were treated by complete excision of the cyst and replacement by a cortico-medullar autogenous graft.

The cytoarchitecture of the dorsal cochlear nucleus in the 3-month- and 26-month-old C57BL/6 mouse: a Golgi impregnation study

The cytoarchitecture of the dorsal cochlear nucleus (DCN) was compared in 3- and 26-month-old C57BL/6 mice. The effects of genetically controlled progressive hearing loss present in the CNS in this mouse strain were analyzed with Nissl-stained and Golgi-impregnated material. The DCN was divided into the superficial molecular, an intermediate fusiform-granule, and the deep polymorphic layers. The molecular layer (ML) consisted of many fibers and a few small ovoid to spherical, fusiform, and granule cells. The fusiform-granule layer (FL) contained large fusiform and many granule cells. Most FL fusiform cells were oriented with their long axes perpendicular to the DCN surface and were present as small aggregations or individually. Cartwheel cells were adjacent to the FL fusiform cells. The deep polymorphic layer (PL) contained spherical, fusiform, granule, and multipolar neurons. The granule cells formed a dorsal cap of the DCN. From this cap, sheets of granule cells separated the DCN from the posterior ventral cochlear nucleus (PVCN) and from the brainsteM. The internal organization, neuronal location, orientation, and morphology were similar in both age groups. The granule cells had four to five primary dendrites, varicosities, and few to no dendritic appendages. The FL fusiform cells displayed different dendritic morphology in the two ages. One or two elaborate primary ML apical dendrites in the 3-month-old mice were covered with spikelike dendritic spines. The basal one or two PL dendrites were less elaborate and had few dendrite spines. In contrast, FL fusiform neurons in 26-month-old mice had regular dendritic varicosities and fewer spines which were short and stumpy. Basal dendrites had varicosities and interruptions. Cartwheel neurons in 3-month-old mice had elaborate ML dendritic trees covered with dendritic spines. In 26-month-old mice the dendrites had many varicosities and fewer short blunted dendritic spines. Large multipolar neurons in older mice had thinner dendrites with more varicosities than were in the 3-month group. In both age groups multipolar cells had few dendritic spines limited distally. Small and large spherical cells had two to five primary dendrites with varicosities, little higher-order branching, and spines. Fusiform cells had one or two primary dendrites, little secondary branching, and few to no spines. Minor degenerative changes were noted in spherical and fusiform cells in the two age groups. These included dendritic varicosities, interruptions, and some irregularities of somata surface. Degenerative changes present in the cochlea had significant effects on a limited population of DCN neurons. Finally, the neuronal morphology and architecture of the DCN in C57BL/6 mouse is similar to other mammalian species.

Angulated bone peg

The use of an angulated bone peg in arthrodesis of a digital joint is presented. The technique was demonstrated in two patients with severe bone loss. A bone graft was fashioned into an angulated peg of the desired angle and size and inserted in both sides of the gap. The suggested technique preserves the finger's length, maintaining the necessary angulation, and provides adequate fixation.

Distraction-lengthening of digital rays in the management of the injured hand

The distraction-lengthening principle and apparatus, formerly used in the hand for reconstruction in congenital anomalies and traumatic amputations, is described for reconstruction of metacarpals and phalanges shortened by injuries, especially gunshot wound, where those bones have lost significant length. Hands in which single metacarpals have been shortened or in which multiple digits are involved may benefit from the technique.

Experience with distraction lengthening of digital rays in congenital anomalies

To improve function and appearance of the hands in 11 children with congenital hypoplasia or aplasia of the digits, the method of distraction lengthening of remaining metacarpal structures was used. Four illustrative cases are discussed in detail.

False aneurysm of the digital artery

A case of false aneurysm of the digital artery is described. To the best of our knowledge it is the first reported case of false aneurysm involving the thumb. The aetiological factors which are usually responsible for the development of a false aneurysm are briefly discussed. The most common factor seems to be a direct injury of the arterial wall by a sharp tool and continuing flow of the blood in the artery. Although the fingers are commonly exposed to injuries with sharp tools, development of a false aneurysm in them seems to be extremely rare.

Osteoarthritis at the base of the thumb. The concept of monoarticular reconstruction

Osteoarthritic affection of the base of the thumb involving 148 hands has been studied. Isolated osteoarthritis of the trapezio-metacarpal joint was found to be the largest group including a total of 111 hands. Reconstruction of this particular joint by a new technique is described and long-term results reported. A small series of isolated osteoarthritis of the trapezio-scaphoid joint is presented and reconstruction by replacing the affected articular surface of the carpal scaphoid is described. Osteoarthritic involvement of more than one of the articular surfaces of the trapezium was found in a group of 31 hands. In all of them the trapezio-metacarpal joint was predominantly affected. The rationale for monoarticular reconstruction of the trapezio-metacarpal joint, regardless of the extent of involvement, is discussed in detail.