Longitudinal profiling identifies co-occurring BRCA1/2 reversions, TP53BP1, RIF1 and PAXIP1 mutations in PARP inhibitor-resistant advanced breast cancer.

BACKGROUND: Resistance to therapies that target homologous recombination deficiency (HRD) in breast cancer limits their overall effectiveness. Multiple, preclinically validated, mechanisms of resistance have been proposed, but their existence and relative frequency in clinical disease are unclear, as is how to target resistance. PATIENTS AND METHODS: Longitudinal mutation and methylation profiling of circulating tumour (ct)DNA was carried out in 47 patients with metastatic BRCA1-, BRCA2- or PALB2-mutant breast cancer treated with HRD-targeted therapy who developed progressive disease-18 patients had primary resistance and 29 exhibited response followed by resistance. ctDNA isolated at multiple time points in the patient treatment course (before, on-treatment and at progression) was sequenced using a novel >750-gene intron/exon targeted sequencing panel. Where available, matched tumour biopsies were whole exome and RNA sequenced and also used to assess nuclear RAD51. RESULTS: BRCA1/2 reversion mutations were present in 60% of patients and were the most prevalent form of resistance. In 10 cases, reversions were detected in ctDNA before clinical progression. Two new reversion-based mechanisms were identified: (i) intragenic BRCA1/2 deletions with intronic breakpoints; and (ii) intragenic BRCA1/2 secondary mutations that formed novel splice acceptor sites, the latter being confirmed by in vitro minigene reporter assays. When seen before commencing subsequent treatment, reversions were associated with significantly shorter time to progression. Tumours with reversions retained HRD mutational signatures but had functional homologous recombination based on RAD51 status. Although less frequent than reversions, nonreversion mechanisms [loss-of-function (LoF) mutations in TP53BP1, RIF1 or PAXIP1] were evident in patients with acquired resistance and occasionally coexisted with reversions, challenging the notion that singular resistance mechanisms emerge in each patient. CONCLUSIONS: These observations map the prevalence of candidate drivers of resistance across time in a clinical setting, information with implications for clinical management and trial design in HRD breast cancers.

Bone marrow mononuclear cell therapy in ischaemic stroke: a systematic review.

Bone marrow mononuclear cell (BM-MNC) therapy has emerged as a potential therapy for the treatment of stroke. We performed a systematic review of published studies using BM-MNC therapy in patients with ischaemic stroke (IS). Literature was searched using MEDLINE, PubMed, EMBASE, Trip Database, Cochrane library and clinicaltrial.gov to identify studies on BM-MNC therapy in IS till June, 2016. Data were extracted independently by two reviewers. STATA version 13 was used for carrying out meta-analysis. We included non-randomized open-label, single-arm and non-randomized comparative studies or randomized controlled trials (RCTs) if BM-MNCs were used to treat patients with IS in any phase after the index stroke. One randomized trial, two non-randomized comparative trials and four single-arm open-label trials (total seven studies) involving 227 subjects (137 patients and 90 controls) were included in the systematic review and meta-analysis. The pooled proportion for favourable clinical outcome (modified Rankin Scale score ≤2) in six studies involving 122 subjects was 29% (95% CI 0.16-0.43) who were exposed to BM-MNCs and pooled proportion for favourable clinical outcome of 69 subjects (taken from two trials) who did not receive BM-MNCs was 20% (95% CI 0.12-0.32). The pooled difference in the safety outcomes was not significant between both the groups. Our systematic review suggests that BM-MNC therapy is safe up to 1 year post-intervention and is feasible; however, its efficacy in the case of IS patients is debatable. Well-designed randomized controlled trials are required to provide more information on the efficacy of BM-MNC transplantation in patients with IS.

Even "Cementless" Surgeons Use Cement.

BACKGROUND: Patients presenting with hip arthritis have huge variability in anatomy, bone quality, and functional expectation. These can contribute to a varying degree of complexity on both the femoral and acetabular sides. Surgeons should be aware of all the various options in fixation, bearing surface, and surgical technique. METHODS: In this article, based on a presentation given at the recent American Association of Hip and Knee Surgeons meeting in Dallas, we will discuss why and how cemented fixation can, and indeed should, be considered when making decisions regarding how a primary, complex primary, or revision hip arthroplasty should be performed. RESULTS: We will review the evidence, surgical technique, and indications for cemented fixation in primary and complex primary surgery. In addition, we will discuss the potential benefits at revision of previous cemented fixation. CONCLUSION: We hope to support the concept that even cementless surgeons should also use cement.

Nutrient intake, digestibility and performance of Gaddi kids supplemented with tea seed or tea seed saponin extract.

OBJECTIVE: An experiment was conducted to determine the nutrient intake, digestibility, microbial protein synthesis, haemato-biochemical attributes, immune response and growth performance of Gaddi kids fed with oat fodder based basal diet supplemented with either tea seed or tea seed saponin (TSS) extract. METHODS: Eighteen male kids, 7.03±0.16 months of age and 19.72±0.64 kg body weight, were distributed into three groups, T0 (control), T1, and T2, consisting of 6 animals each in a completely randomized design. The kids were fed a basal diet consisting of concentrate mixture and oat fodder (50:50). Animals in group III (T2) were supplemented with TSS at 0.4% of dry matter intake (DMI), and group II (T1) were supplemented with tea seed at 2.6% of DMI to provide equivalent dose of TSS as in T2. Two metabolism trials were conducted, 1st after 21 days and 2nd after 90 days of feeding to evaluate the short term and long term effects of supplementation. RESULTS: The tea seed (T1) or TSS (T2) supplementation did not affect DMI as well as the digestibility of dry matter, organic matter, crude protein, neutral detergent fibre, and acid detergent fibre. Nutritive value of diet and plane of nutrition were also comparable for both the periods. However, the average daily gain and feed conversion ratio (FCR) were improved (p<0.05) for T1 and T2 as compared to T0. The microbial protein supply was also higher (p<0.05) for T1 and T2 for both the periods. There was no effect of supplementation on most blood parameters. However, the triglyceride and low density lipoprotein cholesterol levels decreased (p<0.05) and high density lipoprotein-cholesterol level increased (p<0.05) in T2 as compared with T0 and T1. Supplementation also did not affect the cell mediated and humoral immune response in goats. CONCLUSION: Tea seed at 2.6% of DMI and TSS at 0.4% DMI can be fed to Gaddi goats to improve growth rate, FCR and microbial protein synthesis.

Role of prophylactic antibiotics in lesser toe fusion surgery: A prospective randomised controlled trial.

BACKGROUND: This prospective randomised controlled trial was performed to determine whether the incidence of local infection is reduced in patients who are administered prophylactic antibiotics for lesser toe fusion surgery. METHODS: 100 adult patients undergoing toe fusion surgery that required K-wires to be left in situ for 4-6 weeks were randomly allocated into those who received prophylactic antibiotics (Group 1, n=48) and those who did not (Group 2, n=52). Patients were followed up regularly and during each visit K-wire insertion sites were assessed for signs of pin tract infection. RESULTS: The mean age of Group 1 was 58.0 (SD 17.5) and Group 2 was 62.7 years (SD 14.7). The overall infection rate was 4%. Three patients (6.2%) in Group 1 and one patient (1.9%) in Group 2 developed signs of infection, which required treatment by oral antibiotics. All infections were low grade. There were no features suggestive of osteomyelitis in any of the patients. CONCLUSION: The overall infection rate in lesser toe fusion surgery is low and that using prophylactic antibiotics does not reduce the incidence. Inappropriate use of antibiotics, however, may contribute to the development of antibiotic resistance and adds to healthcare costs.

Is an online skin cancer toolkit an effective way to educate primary care physicians about skin cancer diagnosis and referral?

BACKGROUND: Skin disorders account for over 20% of GP consultations. Half of dermatology referrals to secondary care are for skin lesions, but only 12% of urgent skin cancer referrals are deemed appropriate. Suitably designed online learning resources may positively impact GP confidence in the recognition of skin cancer and improve patient outcomes. OBJECTIVE: This study evaluated the impact of a national, online, skin cancer recognition toolkit on GP confidence and knowledge in diagnosing skin cancers and referral behaviour to secondary care. METHODS: The toolkit, consisting of a referral decision aid, lesion recognition resource, clinical cases and a quiz, was launched in March 2012. Website usage statistics and online focus groups were used to assess the usability of the website and perceived changes in behaviour. The impact of the toolkit was assessed using national skin cancer referral data, cross-sectional questionnaires and urgent skin cancer referral data to two NHS trusts. RESULTS: The toolkit was accessed by 20% of GPs in England from 20th March to 31st October 2012; spending a mean of over 5 minutes each, with over 33% return users. A survey revealed that the toolkit improved perceptions of skin cancer training and self-reported knowledge about skin cancer referral pathways. Analysis of referral patterns did not identify an impact of the toolkit on number or appropriateness of urgent skin cancer referrals in the eight months following the launch of the website. Online focus groups confirmed the usefulness of the resource and suggested a positive influence on knowledge and referral behaviour. CONCLUSION: The skin cancer toolkit is an accessible online learning resource for improving confidence with skin cancer referral amongst GPs. Although we were unable to identify any immediate changes in skin cancer diagnoses or appropriate referral behaviours, research is required to evaluate its longer term effects on outcomes.

In vitro antimicrobial activity of crude ethanol extracts and fractions of Terminalia catappa and Vitex doniana.

BACKGROUND: The spread of microorganisms resistant to some antimicrobial agents necessitates the need to search for novel and effective antimicrobial agents. In this study, the antimicrobial activity of Terminalid catappa Linn. (Combretaceae) and Vitex doniana Sweet. (Verbenaceae), two Nigerian medicinal plants used in folk medicines for the management of various ailments related to microbial infections were evaluated. OBJECTIVES: To evaluate the antimicrobial activity of the crude ethanol extracts and fractions of the leaves and stem bark of T. catappa and V. doniana. METHODOLOGY: Four crude ethanol extracts and 16 (n-hexane, ethylacetate, n-butanol and aqueous) fractions of leaves and stem bark of T. catappa and V doniana were evaluated for in vitro antimicrobial activity against fifteen (15) strains of bacteria and fungi. The antimicrobial activity was determined in a 96-well plate using a resazurin based broth microdilution method. Two standard antimicrobial drugs ampicillin and nystatin were included as positive control. RESULTS: The butanoL fraction of stem bark of T. catappa and ethanol crude extract of leaf of V don iana displayed the highest antibacterial activity with similar minimum inhibitory concentration (MIC) value of 93.75 microg/mL against S. aureus and B. subtilis. Furthermore, the ethyl acetate fraction of stem bark of T. catappa showed the highest antifungal activity with MIC of 187.5 microg/mL against A. sydowi. Amp icillin had MIC of 15.6 and 31.3 microg/mL against S. aureus and B. subtili, respectively while nystatin produced MIC of 3.9 microg/mL against A. sydowi. CONCLUSION: Termninalia catappa and Vitex doniana may serve as useful sources of plant derived antimicrobial agents.

Key differences identified between actinic keratosis and cutaneous squamous cell carcinoma by transcriptome profiling.

BACKGROUND: Cutaneous squamous cell carcinoma (cSCC) is one of the most common malignancies in fair-skinned populations worldwide and its incidence is increasing. Despite previous observations of multiple genetic abnormalities in cSCC, the oncogenic process remains elusive. The purpose of this study was to elucidate key molecular events associated with progression from premalignant actinic keratoses (AKs) to invasive cSCC by transcriptome profiling. METHODS: We combined laser capture microdissection with the Affymetrix HGU133 Plus 2.0 microarrays to profile 30 cSCC and 10 AKs. RESULTS: We identified a core set of 196 genes that are differentially expressed between AK and cSCC, and are enriched for processes including epidermal differentiation, cell migration, cell-cycle regulation and metabolism. Gene set enrichment analysis highlighted a key role for the mitogen activated protein kinase (MAPK) pathway in cSCC compared with AK. Furthermore, the histological subtype of the tumour was shown to influence the expression profile. CONCLUSION: These data indicate that the MAPK pathway may be pivotal to the transition from AK to cSCC, thus representing a potential target for cSCC prevention. In addition, transcriptome differences identified between cSCC subtypes have important implications for future development of targeted therapies for this malignancy.

Renal angioplasty for atherosclerotic renal artery stenosis: Cardiologist's perspective.

Atherosclerotic renal artery stenosis (ARAS) is frequently associated with concomitant coronary and peripheral arterial disease with a significant impact on cardiovascular morbidity and mortality. Renal angioplasty of ARAS is more challenging because of increased incidence of technical failures, complications, and restenosis; while there is barely perceptible control of hypertension and only marginal improvement in renal function. This is because most of the patient population in recent randomized trials had unmanifested or clinically silent renovascular disease. Manifestations of RAS should be looked for and incorporated in the management plan particularly before deciding for revascularization. In the absence of clinical manifestation like renovascular hypertension, ischemic nephropathy, left ventricular failure, or unstable coronary syndromes; mere presence of RAS is analogous to presence of concomitant peripheral arterial disease which increases risk of adverse coronary events. Dormant-RAS in the absence of any manifestations can be managed with masterly inactivity. Chronological sequence of events and clinical condition of the patient help in decision making by identifying progressive renovascular disease. Selecting patients for renal artery stenting who actually will benefit from revascularization shall also decrease the unnecessary complications inherent with any interventional procedure. The present review is an attempt to analyze the current view on the diagnostic and management issues more specifically about the need and rationale behind angioplasty.

Brucella endocarditis - a series of five case reports.

Endocarditis due to brucellosis is considered a rare occurrence involving native, congenital and prosthetic valves. The diagnosis needs high degree of suspicion in culture negative endocarditis especially in those with history of exposure to farm animals. A positive culture in a susceptible patient confirms the diagnosis with 91% sensitivity. An early diagnosis and prompt treatment with appropriate antibiotics can restore the valve structural integrity with minimal damage. Here we present a series of five cases of culture proven Brucella endocarditis (four native valves, one prosthetic valve) and this report discusses the diagnostic and management issues involved.

Residual unabsorbed midazolam: a case report.

BACKGROUND: Oral midazolam is commonly administered to reduce anxiety in children presenting for medical procedures or surgery. It is unclear what volume of medication remains unabsorbed in the stomach when the child presents for anesthetic induction prior to these procedures. The presence of any significant residual medication in the stomach has significant clinical implications in the postoperative period. CASE PRESENTATION: A 5-year-old white Caucasian boy presented for upper gastrointestinal endoscopy after receiving oral midazolam liquid. Insertion of the endoscope into the stomach revealed a significant amount of unabsorbed medication remaining within the gastric cavity. CONCLUSION: Clinicians should be aware that the sedative effects of midazolam may be present before the medication is fully absorbed. A significant amount of unabsorbed medication may be present in the stomach during medical procedures/surgery. This may continue to be absorbed in the intraoperative and postoperative period, with unwanted clinical effect.

Patient perspectives on elective orthopaedic surgery during the COVID-19 pandemic: a comparison between patients from different ethnic backgrounds.

INTRODUCTION: Suspending elective surgery during the first wave of coronavirus (COVID-19) led to record-breaking numbers of patients on waiting lists. Patients in Black, Asian and minority ethnic (BAME) groups are disproportionately affected by COVID-19. This study compares the perspectives of patients from different ethnic backgrounds on the return to elective surgery. METHODS: Some 151 patients were sampled from cancelled operating lists at two hospitals. Semi-structured interviews focused on the impact of COVID-19, and views about resuming elective surgery. The Generalized Anxiety Disorder 7-iten Scale (GAD-7) measured anxiety. A visual analogue scale (VAS) measured pain. Data were analysed using exploratory thematic analysis. RESULTS: Fewer BAME patients were pleased about restarting surgery, compared with white patients (47.3% vs 82.6%, p<0.001), and a greater proportion wanted to postpone their operation until after the pandemic (21.8% vs 9.3%, p=0.048). White/white British patients had higher GAD-7 scores (2 (0-21) vs 0 (0-16), p=0.009). Black/Black British patients had significantly higher VAS scores compared with white/white British and Asian/Asian British patients (85 vs 75 vs 70 respectively, p<0.05). CONCLUSION: The delay in surgery due to the pandemic has had a devastating impact on patients awaiting operations. The variation in pain and anxiety levels between ethnic groups must be addressed when redesigning services to avoid discrepancies in postoperative clinical outcomes. Patients in BAME groups are more likely to postpone their operation, which may lead to further health deterioration, psychosocial and socio-economic consequences, and poorer clinical outcomes following surgery. The thoughts, feelings and concerns of all must be considered when redesigning services to prevent health inequalities between patients from different backgrounds.

Functional outcome and discharge destination in elderly patients with spinal cord injuries.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To describe functional outcome and discharge destination of elderly patients with traumatic spinal cord injuries. SETTING: National Spinal Injuries Unit, Glasgow, UK. METHODS: We collected data for 5 years on all patients >65 years old with a traumatic spinal cord injury treated at the National Spinal Injuries Unit. RESULTS: We identified 39 patients. Of these, nine patients died during admission; all had cervical spine injuries. The mean age of the 30 survivors was 73 years (range 65-88). The most common cause of injury was a fall: 26 patients (87%). In addition, 21 (70%) sustained injury to cervical cord, 3 (10%) had thoracic and 6 (20%) had lumbar spine fractures. In all, 23 patients (77%) were treated by orthosis and 7 (23%) underwent surgical intervention. Twelve (40%) patients showed an improvement in American Spinal Injury Association impairment scale. The median hospital stay was 136 days. Thus, 11 patients (37%), all with incomplete injuries, were discharged home, 10 (33%) were transferred to nursing homes/community hospitals and 9 patients (30%) were discharged back to the referring hospital, while they were awaiting adjustments at home. Patients who were discharged home had significantly higher Functional Independence Measure scores, both at the onset of rehabilitation and at discharge, than those who were discharged to a nursing home or other hospitals (P<0.01 and <0.001, respectively). DISCUSSION AND CONCLUSION: Although the elderly patients may benefit from the services of a dedicated spinal injuries centre, they should be carefully selected. The patient, relatives as well as the referring doctors should be alerted to the likely long-term outcomes early in the course of the injury. Elderly patients with complete lesions of the spinal cord will almost certainly remain institutionalized. Early endeavour should be made to find alternate rehabilitation settings with a lower-intensity treatment.

A survey on the management of acute rhinosinusitis among Asian physicians.

BACKGROUND: Based on the `European Position Paper on Rhinosinusitis and Nasal polyps (EP3OS 2007)`, this study aimed to investigate general practitioners (GPs) and other specialists` understanding when managing patients with acute rhinosinusitis (ARS) in Asia. METHODOLOGY: Among a total of 2662 questionnaires completed, 2524 (94.8%) were valid for analysis. There were 1308 GPs (51.8%), 989 otolaryngologists (39.2%) and 227 paediatricians (9%) from Mainland China, Hong Kong, Indonesia, India, Malaysia, Pakistan, Philippines, Singapore, Thailand and Taiwan. RESULTS: ARS is affecting an estimated 6 - 10% of patients seen in a daily out-patient practice. The EP3OS criteria are well supported by Asian physicians (94.1%). Most physicians (62.7%) agreed that radiological investigation is not needed to diagnose ARS. However, even for mild ARS (common cold), medical treatments were still recommended by 87% of GPs, 83.9% of otolaryngologists, and 70% of paediatricians. The top three first-line treatments prescribed were antihistamines (39.2%), nasal decongestants (33.6%), and antibiotics (29.5%). Antibiotics usage increased as the first line treatment of moderate (45.9%) and severe (60.3%) ARS. CONCLUSION: ARS is commonly managed by GPs, otolaryngologists, and paediatricians in Asia. However, understanding of the management of ARS needs further improvement to minimize unnecessary use of radiological investigations, overuse of antibiotics, and under use of nasal corticosteroids.

Lateral segmental mandibulectomy reconstruction with bridging reconstruction plate and anterolateral thigh free flap: a case series of 30 consecutive patients.

Lateral posterior segmental mandibular defects present a reconstructive challenge and an osseous flap would be the gold standard to reconstruct such a defect. However, combining a mandibular reconstruction plate (MRP) with a soft-tissue free flap (to restore mucosal integrity and provide durable coverage of the plate itself) offers an alternative option for posterior segmental mandibular defects in patients who are not suitable for osseous reconstruction, or do not choose it. We retrospectively reviewed 30 consecutive patients (19 male and 11 female) who underwent reconstruction of a segmental mandibulectomy defect using a bridging MRP and anterolateral thigh (ALT) free flap. The mean (range) age was 67 (31-87) years. The American Society of Anesthesiologists' (ASA) status of the study population comprised Grade 1 (n = 10), Grade 2 (n = 18), and Grade 3 (n = 2). The majority of patients had oral cavity squamous cell carcinoma (n = 26) involving the mandible, two had osteoradionecrosis, and two mucoepidermoid carcinoma. Four patients had complications specific to the reconstruction, and flap loss occurred in one (96.7% success rate). Metalwork infection occurred in three, including one plate extrusion and one plate fracture. The median length of stay was 10 days, and mean (range) duration of follow up 23.3 (1-96) months. This technique is an alternative reconstructive option for the non-tooth-bearing mandible. Reconstructing a posterolateral segmental mandibulectomy defect with a bridging MRP and ALT free flap offers a robust reconstructive alternative with a favourable complication profile.

Challenges and outcomes in establishing a sentinel lymph node biopsy service for oral squamous cell carcinoma in a regional district specialist hospital.

UK national guidelines in 2016 recommended that sentinel lymph node biopsy (SLNB) should be offered to patients with early oral squamous cell carcinoma (OSCC). We review the establishment of an OSCC SLNB service with specific consideration to resources, service implications and patient outcomes. A review of processes was performed to identify key stages in establishing the service, and subsequently a retrospective cohort study consisting of 46 consecutive patients with T1/T2 N0 OSCC was undertaken. The key stages identified were: coordinating a nuclear medicine pathway and reliable cost-appropriate pathology service, constructing a Trust business case, and gaining approval of a new interventional service policy. A median (range) of 3.3 (1-8) sentinel nodes (SLN) were removed, with 17 patients having a positive SLN. The negative predictive value of SLNB was 100%, with 12 having a SLN outside the field if elective neck dissection (END) was planned. There was a significantly increased risk of a positive SLN with increasing depth of invasion (DOI) (p=0.007) and increased diameter (p=0.036). We also identified a longer-than-ideal time to completion neck dissection and inadequate ultrasound follow up of negative SLNB patients. Establishment of a service requires careful planning. Our results were in keeping with those reported in the literature, and showed that SLNB for OSCC has a high negative predictive value and can identify at-risk SLN outside the traditional END levels, even in well-lateralised tumours. Our findings show that DOI and size of SLN were significantly associated with a positive SLN, and also identified areas requiring improvement.

Use of Contegra conduit reinforced with Goretex as a modified left Blalock-Taussig shunt.

This is the first report of the construction of a modified Blalock-Taussig shunt using a Contegra conduit reinforced with Goretex in a 4-year-old boy. The patient had a complex cardiac history with a primary diagnosis of pulmonary atresia, hypoplastic right ventricle (RV) and RV-coronary artery fistula.

Patients undergoing primary surgery for oral and oropharyngeal cancer: how many are referred on the two-week wait pathway and by whom?

INTRODUCTION: Available data suggest that the two-week wait referral pathway is ineffective at expediting diagnosis of cancer due to large numbers of inappropriate referrals. This study aimed to compare the referral pathway of 125 patients who had undergone primary surgery for oral and oropharyngeal cancer with 100 who had been two-week wait referrals. MATERIALS AND METHODS: This was a case note review. RESULTS: Of the 125 patients who underwent surgery; 47 (38%) were referred via the 2WW pathway. GPs had referred 25 (53%) of the 47 patients and general dental practitioners 22 (47%). The tumour stage was similar regardless of referral pathway (two-week wait or routine). GPs recognised that the two-week wait pathway was needed in 49% of the patients they had referred, whereas the equivalent figure for GDPs was 40%. Of the 100 2WW patients, 52 were biopsied. Of these, nine (9%) were diagnosed with a malignancy. GPs referred 61% of the 100 two-week wait patients and accurately diagnosed five of the cancers (although two were basal cell carcinomas), general dental practitioners the remainder (including one basal cell carcinoma). Overall, 41% of the patients referred on the two-week wait pathway by GPs needed a biopsy, compared with 69% of those referred by general dental practitioners. CONCLUSIONS: While the criteria for referral on the two-week wait pathway lack discrimination and the majority of referrals proved benign, nearly 40% of surgically treated patients were referred via this pathway, suggesting that it does serve a useful purpose. More patients with cancer were referred by GPs, but more two-week wait referrals by general dental practitioners warranted biopsy.

Changes in the basement membrane zone components during skeletal muscle fiber degeneration and regeneration.

The basement membrane of skeletal muscle fibers is believed to persist unchanged during myofiber degeneration and act as a tubular structure within which the regeneration of new myofibers occurs. In the present study we describe macromolecular changes in the basement membrane zone during muscle degeneration and regeneration, as monitored by immunofluorescence using specific antibodies against types IV and V collagen, laminin, and heparan sulfate proteoglycan and by the binding of concanavalin A (Con A). Skeletal muscle regeneration was induced by autotransplantation of the extensor digitorum longus muscle in rats. After this procedure, the myofibers degenerate; this is followed by myosatellite cell activation, proliferation, and fusion, resulting in the formation of new myotubes that mature into myofibers. In normal muscle, the distribution of types IV and V collagen, laminin, heparan sulfate proteoglycan, and Con A binding was seen in the pericellular basement membrane region. In autotransplanted muscle, the various components of the basement membrane zone disappeared, leaving behind some unidentifiable component that still bound Con A. Around the regenerated myotubes a new basement membrane (zone) reappeared, which persisted during maturation of the regenerating muscle. The distribution of various basement membrane components in the regenerated myofibers was similar to that seen in the normal muscle. Based on our present and previous study (Gulati, A.K., A.H. Reddi, and A.A. Zalewski, 1982, Anat. Rec. 204:175-183), it appears that some of the original basement membrane zone components disappear during myofiber degeneration and initial regeneration. As a new basement membrane develops, its components reappear and persist in the mature myofibers. We conclude that skeletal muscle fiber basement membrane (zone) is not a static structure as previously thought, but rather that its components change quite rapidly during myofiber degeneration and regeneration.

Physiological migration of hematopoietic stem and progenitor cells.

Hematopoietic stem cells (HSCs) reside predominantly in bone marrow, but low numbers of HSCs are also found in peripheral blood. We examined the fate of blood-borne HSCs using genetically marked parabiotic mice, which are surgically conjoined and share a common circulation. Parabionts rapidly established stable, functional cross engraftment of partner-derived HSCs and maintained partner-derived hematopoiesis after surgical separation. Determination of the residence time of injected blood-borne progenitor cells suggests that circulating HSCs/progenitors are cleared quickly from the blood. These data demonstrate that HSCs rapidly and constitutively migrate through the blood and play a physiological role in, at least, the functional reengraftment of unconditioned bone marrow.