Pancreatic exocrine insufficiency in HIV-positive patients

OBJECTIVES

We describe the management of a cohort of eight HIV-positive patients on antiretroviral medication with evidence of pancreatic insufficiency consisting of chronic diarrhoea and a low faecal elastase measurement.

PATIENTS AND METHODS

Twenty-two patients with chronic diarrhoea for whom a faecal elastase measurement was available were identified retrospectively. We compared baseline demographic characteristics, antiretroviral treatment and symptoms of steatorrhea between patients with evidence of pancreatic insufficiency, i.e. a low faecal elastase measurement of <200 microg/g (cases), and patients with evidence of normal pancreatic function, i.e. a normal faecal elastase measurement of >200 microg/g (controls). We describe the management of the patients with evidence of pancreatic insufficiency.

RESULTS

Of the 22 patients, eight had evidence of pancreatic insufficiency, i.e. a low faecal elastase measurement. Comparing cases with controls, cases were more likely to have symptoms of steatorrhea (P=0.03) or to have lost weight (P=0.02). Cases were also significantly more likely to have taken didanosine (ddI) as part of their antiretroviral treatment when their symptoms started. Seven cases were treated with oral pancreatic supplements and all had symptomatic improvement of their diarrhoea. One patient stopped treatment with oral pancreatic supplements because of side effects without a relapse of symptoms; he had also stopped zalcitabine (ddC).

CONCLUSIONS

We believe that measurement of faecal elastase to detect pancreatic insufficiency should be part of the standard investigation of HIV-positive patients with chronic diarrhoea alongside assessment for other causes of diarrhoea. Faecal elastase measurements should be requested, in particular, in all patients with diarrhoea and weight loss, or symptoms of steatorrhea, and in those on treatment with an antiretroviral regime containing ddI. If the faecal elastase level is low, a switch of antiretroviral medication to a nonddI/ddC-containing regime should be considered and treatment with oral pancreatic enzyme therapy should be instituted.

HIV viral suppression in the era of antiretroviral therapy

Altogether 42 million people worldwide have been infected with HIV, and 12 million have died over the last 20 years. Effective antiretroviral therapy has lead to sustained HIV viral suppression and immunological recovery in patients who have been infected with the virus. The incidence of AIDS has declined in the Western world with the introduction of effective antiretroviral therapy. Questions on When to start treatment?, What to start with?, How to monitor patients?, remain heavily debated. Adherence to antiretroviral treatment remains the cornerstone of effective treatment, and failure to adhere is the strongest predictor of virological failure. Long term therapy can lead to metabolic complications. Resource poor countries are dealing with difficult issues such as mother to child prevention of HIV transmission. Other treatment options are now available, with the recent introduction of fusion inhibitors, second generation non-nucleoside reverse transcriptase inhibitors, and nucleotide reverse transcriptase inhibitors to clinical practice.

Oral cancer, fever of unknown origin, and listeriosis

Listeriosis is a rare cause of fever of unknown origin in patients with oral cancer. We report two patients who, because of pain and discomfort, ate large quantities of soft cheeses; this caused listeriosis and fever. Both cases responded to high doses of amoxycillin.

Pneumocystis carinii pneumonia after thoracic duct ligation and leakage

A case of Pneumocystis carinii pneumonia was induced through immunosuppression following thoracic duct ligation. The patient initially presented with an esophageal adenocarcinoma, which was totally resected. She is human immunodeficiency virus-negative and not undergoing immunosuppressive treatment.

Activity-induced fiber regeneration in rat soleus muscle

In an attempt to understand why muscle recovery is limited following atrophy due to limb immobilization, satellite cell activity and muscle fiber regeneration were analyzed in rat soleus muscles. Adult rat hindlimbs were immobilized in plaster casts for a period of two to ten weeks. Soleus muscles were examined by electron microscopy for evidence of fiber degeneration or regeneration, and to quantify satellite cell nuclei. Immunocytochemical localization of embryonic myosin was used to identify regenerating myofibers. Soleus muscle wet weight to body weight ratios for the casted muscles significantly decreased over the 10-week immobilization period. The casted muscles displayed ultrastructural evidence of minor fiber damage, including myofibrillar atrophy, Z-disc disruption, and abnormal triadic junctions. No ultrastructural evidence of regeneration was seen in the casted animals. The number of satellite cells in the casted muscles significantly decreased from 6.4% to 3. 3% by eight to 10 weeks of immobilization. Approximately 1.0% of extrafusal fibers in the control soleus muscles appeared to be regenerating since they expressed embryonic myosin and were of a small diameter, while in casted muscles, only 0.1% of the fibers were embryonic myosin-positive. Following release from immobilization, a reappearance of embryonic myosin-positive fibers was noted within four days of renewed activity. In contrast to control muscles, embryonic myosin-positive fibers in the recovery muscles included both small and large diameter fibers. Subtle changes in functional activity influence muscle damage and subsequent myofiber regeneration. Reduced activity reduces muscle fiber regeneration, while increased activity, as seen by increased hindlimb weight bearing and return to normal activity following immobilization, increase regenerating fibers and also the expression of embryonic myosin in adult fibers.

Primary tuberculosis of the posterior oropharyngeal wall

We report a case of primary tuberculosis of the posterior oropharyngeal wall presenting with sore throat, fever and malaise. Pharyngeal tuberculosis is rare and usually occurs with primary pulmonary disease. Primary disease has been reported in small numbers in the nasopharynx and palatine tonsil but never before, to our knowledge, in the posterior oropharyngeal wall.

The role of disclosure in coping with HIV infection

A qualitative investigation was conducted to explore the role of disclosure in HIV infection. Forty homosexual and bisexual men completed a short demographic questionnaire and participated in a one-to-one, semi-structured interview. The interview was designed to address a variety of personal, interpersonal and organizational issues related to their HIV status and participants were invited to talk about their personal experiences from immediately prior to their diagnosis to the time of the interview. The results from the interviews are presented in three sections: immediately post-diagnosis, asymptomatic phase and symptomatic/AIDS phases. The data revealed that disclosing one's HIV status was an acute and recurrent stressor. Immediately post-diagnosis, individuals were more likely to adopt a policy of non-disclosure and this provided them with an opportunity to come to terms with their diagnosis before having to contend with the reactions of others. After this phase, there was evidence that individuals increasingly used disclosure as a mechanism for coping with the disease. Disclosure of one's status was used to increase both practical and emotional support, share responsibility for sex and to facilitate self-acceptance of one's condition. The results from this investigation revealed that disclosure has a dual role in HIV infection acting as both a stressor and a mechanism by which individuals contend with their infection.

An indolent penile herpetic ulcer in a patient with previously undiagnosed human immunodeficiency virus infection

We report a case of an atypical penile herpetic ulcer in a man with previously undiagnosed human immunodeficiency virus (HIV) infection. Swabs of the lesion were negative for herpes simplex virus (HSV) by culture and electron microscopy. However, histopathology of biopsy material showed characteristic herpetic multinucleate giant cells. Immunochemistry using polyclonal antibodies was positive for HSV1 and HSV2. The lesion completely resolved after treatment with aciclovir and the patient subsequently tested positively for HIV antibodies.

Greater emotional distress is associated with accelerated CD4+ cell decline in HIV infection

An investigation was conducted to explore the relationship between emotional distress and HIV progression. One hundred twenty-five homosexual, HIV-positive males participated in a 12-month longitudinal investigation. Psychosocial data were collected at 6-month intervals and CD4+ data were collected from diagnosis to the end of the investigation. Principal component analyses were performed initially to identify factors of emotional distress and health status. In addition, CD4+ reliability assessments were performed to ensure the validity of the prognostic assessments made. As a result of these analyses, 47 individuals were eligible for the main analyses. The results from a stepwise regression revealed that disease progression was significantly predicted by CD4+ count at diagnosis (32% of variance) and emotional distress (17% of variance), but was unrelated to subjective perceptions of health. The data suggest that some of the variability in HIV progression can be attributed to emotional distress.

Effects of supplemental instruction on mean test scores and failure rates in medical school courses

PURPOSE

To determine whether supplemental instruction offered to first-year medical students reduces the number of examination failures.

METHOD

A student-run, optional, supplemental-instruction program called the Medical Scholars Program (MSP) was offered at no cost to all first-year students at the University of Southern California School of Medicine in 1994-95. Supplemental instruction was offered in a small-group format in biochemistry, gross anatomy, microanatomy, and physiology. Weekly two-hour sessions were conducted by second-year medical students during the first trimester of the year-1 curriculum. Mean test scores and failure rates for students considered academically at risk and those not at risk were compared between the class entering in 1994 and the classes matriculating during the preceding three years. At-risk students were defined as those with a total Medical College Admission Test score below 26 and a science grade-point average below 3.0. Comparisons were performed using two-tailed t-tests and chi-square tests.

RESULTS

Statistically significant increases in mean test scores were achieved on most examinations by the class exposed to the MSP. Failure rates for at-risk students decreased by 46% during the year the MSP was offered.

CONCLUSION

Supplemental instruction can significantly improve student performance and therefore retention, particularly among at-risk students.

Overwhelming pneumoccoccal sepsis in two patients splenectomised more than ten years previously

Asplenic individuals are known to be at a higher risk of developing serious and occasionally fatal sepsis. Prophylactic measures are generally recommended for the first few years post-splenectomy. We report two cases of severe Pneumococcal Sepsis occurring more than 10 years post-splenectomy leading to prolonged hospitalisation and long term morbidity and suggest that Prophylactic Penicillin should be taken life-long.

A technique for accurate use of CD4+ cell counts

Despite uncertainty over their reliability, CD4+ cell counts are used extensively in both clinical and research settings to document progression in HIV infection. We examined, therefore, whether the performance of a simple statistical test would facilitate greater accuracy in the use of this marker. CD4+ cell count data were collected from a cohort of deceased (N = 60) and living HIV-positive gay men (N = 100). Pearson's product moment correlation coefficients were calculated for each individual in order to examine the association between CD4+ counts and time since diagnosis. Correlations of 0.7 or greater were obtained in approximately 50 percent of cases in each cohort. For these individuals, CD4+ cell counts were deemed to be a reliable indicator of rate of progression. The results suggest that the proposed technique ensures greater precision in the use of CD4+ cell counts and that the technique cna be used in individuals with either complete (deceased patients) or partial (living patients) CD4+ data.

Presence of embryonic myosin in normal postural muscles of the adult rat

Indirect immunofluorescence was used to localize embryonic myosin heavy chains in soleus, adductor longus, tibialis anterior, plantaris, and extensor digitorum longus muscles of 6-month-old rats. A monoclonal antibody (2B6), specifically recognizing rat embryonic myosin, was applied to unfixed, transverse, frozen sections. The number of embryonic myosin-positive (EMP) extrafusal fibers was expressed as a percentage of the total number of fibers. EMP extrafusal fibers were only seen in the soleus and adductor longus muscles, both postural muscles. Approximately 1% of the soleus muscle fibers appeared positively stained for embryonic myosin. The majority of such fibers had a small diameter (< 500 mu2), appeared intensely fluorescent, and typically contained central nuclei. Re-expression of embryonic myosin due to spontaneous fiber denervation is not a likely factor in this study, since alpha-bungarotoxin and N-CAM localization were restricted to the motor end-plate region of EMP fibers. Since embryonic myosin was shown to disappear in all normal-sized myofibers by 2 to 3 months of age, the results suggest that the EMP extrafusal fibers seen in postural muscles of 6 to 12-month-old animals are regenerating myofibers. We speculate that a small number of muscle fibers may be regenerating in normal, adult postural muscles, in response to fiber damage possibly caused by excessive recruitment or overloading.

Mortality and survival trends in patients with AIDS in north east England from 1984-1992

OBJECTIVE

to study trends in mortality and survival in patients with AIDS attending an ID unit.

METHOD

retrospective analysis of patients developing an AIDS-defining illness between April 1984, and November 1992. Survival was analysed by calculation of survival product-limit.

RESULTS

71 patients were analysed (including four women), 23 of whom are still alive. Pneumocystis carinii pneumonia (PCP) was the most frequent AIDS-index diagnosis: n = 36 (51%); 24 of these patients have died. HIV encephalopathy was the most frequent diagnosis at death; n = 16 (22.5%), followed by mycobacterial infection; n = 11 (15.5%), and PCP and CMV infection, each occurring in 10 (14%). One-, 2- and 3-year survival probabilities for patients with AIDS before 1987 were 0.46, 0.15 and 0 compared with probabilities of 0.63, 0.5 and 0.3 in those diagnosed after 1987; log rank -P < 0.01. One- and 2-year survival probabilities in patients who received at least 3 months' zidovudine (AZT) therapy were 0.76 and 0.53 in those who are still alive compared with 0.55 and 0.33 in the deceased, while values for deceased AZT-naive patients were 0.29 and 0.1; -P < 0.01. Thirteen (27%) deaths occurred within 2 months of an AIDS-index disease. In 10 patients this was their first presentation to the department. PCP accounted for 8 (61%) of these deaths.

CONCLUSIONS

survival in patients with AIDS has increased since 1987, when AZT was introduced. Early AIDS-related deaths are frequent in patients who have had no prior medical care. This has implications for education and provision of care in individuals with asymptomatic HIV infection.

Giant cell arteritis--A cause of pyrexia of unknown origin

Giant cell arteritis may present atypically with symptoms of malaise, anorexia, weight loss and fever that could lead to diagnostic difficulties. We describe two cases which the prominent initial feature was protracted pyrexia. Clinicians should seriously consider temporal artery biopsy in such cases.

Primordial germ cells in the mouse embryo during gastrulation

With the aid of a whole-mount technique, we have detected a small cluster of alkaline phosphatase (ALP)-positive cells in whole mounts of mid-primitive-streak-stage embryos, 7–7 1/4 days post coitum (dpc). Within the cluster, about 8 cells contain a small cytoplasmic spot, intensely stained for ALP activity and possibly associated with an active Golgi complex. The cluster lies just posterior to the definitive primitive streak in the extraembryonic mesoderm, separated from the embryo by the amniotic fold. Towards the end of gastrulation, the number of cells containing the ALP-positive spot rises to between 50 and 80. Thereafter the number of cells in the extraembryonic cluster declines, and similar cells start to be seen in the mesoderm of the primitive streak and then in the endoderm. At 8 dpc, about 125 ALP-stained cells are found, mainly in the hindgut endoderm and also at the base of the allantois, their appearance and location at this stage agreeing closely with previous reports on primordial germ cells (PGCs). Embryos from which the cluster area has been removed at the 7-day stage are devoid of PGCs after culture for 48 h, whereas the excised tissue is rich in PGCs. We argue that the cells in the cluster are indeed primordial germ cells, at a stage significantly earlier than any reported previously. This would indicate that the PGC lineage in the mouse is set aside at least as early as 7 dpc, possibly as one of the first ‘mesodermal’ cell types to emerge, and that its differentiation, as expressed by ALP activity, is gradual.

Satellite cell response in rat soleus muscle undergoing hypertrophy due to surgical ablation of synergists

Although the role of satellite cells has been confirmed during skeletal muscle growth and regeneration, their involvement during work-induced muscle growth remains uncertain. In this study, chronically overloaded rat soleus muscles were ultrastructurally monitored following surgical ablation of synergists to examine cytological adaptations of satellite cells and myofibers. The left soleus muscle of 20 female Sprague-Dawley rats (7 weeks of age) was induced to hypertrophy by excising the contralateral plantaris and gastrocnemius muscles under pentobarbital anesthesia. Right limbs were sham-operated and served as controls. On days 3, 7, 14, 21, and 30 after surgery, the soleus muscles were removed and processed for electron microscopy. Two morphologically distinct phases were noted in the surgically overloaded muscles. The first stage (week 1) was characterized by a significant increase in the number of satellite cells, and by more than half of the experimental muscle fibers displaying myofibrillar disruptions, mitochondrial alterations and glycogen pooling. The second phase (weeks 2-4) featured mostly normal, although larger appearing muscle fibers, with the satellite cell frequency remaining slightly elevated. These findings suggest that muscle fiber structural abnormalities, rather than an increase in muscle activity, may play a more significant role in the early activation of satellite cells during compensatory hypertrophy, whereas activation of satellite cells during the later stages may be in response to increased levels of muscle activity.

Yersinia pseudotuberculosis infection as a cause of reactive arthritis as seen in a genitourinary clinic: case report

Patients are often referred to the genitourinary clinic for screening for urethral infections after a clinical diagnosis of Reiter's syndrome or reactive arthritis. We report a case of reactive polyarthritis in which serological evidence of Yersinia pseudotuberculosis infection was found in the absence of the other common precipitating organisms, such as Chlamydia spp, Klebsiella spp, Shigella spp, Campylobacter spp, or Yersinia enterocolitica.

Hypercalcaemia in association with enteric fever

We report 2 cases of hypercalcaemia and hypercalciuria, with detectable levels of parathyroid hormone, which appeared to be precipitated by enteric fever. Extensive investigation of one case, including ultrasound, isotope scanning, angiography, computed tomographic scanning and surgical exploration, failed to detect a parathyroid adenoma. In both cases biochemical and hormonal abnormalities resolved several months after recovery of enteric fever. The mechanism of the proposed association is unexplained but it should be considered in any patient with hypercalcaemia and detectable parathyroid hormone levels, who is suffering from or has recently recovered from enteric fever. If such a patient is well, a period of several month's observation is recommended. We believe these two cases to be the first such reports of hypercalcaemia in association with enteric fever.

Early development in the mouse: would it be affected by microgravity?

Gravity has been identified as a morphogenetic signal in Amphibian and bird embryonic development so it is plausible that it might be such in mammals as well. Since early mammalian development shows some apparently significant differences to these other groups, a brief summary of mouse embryogenesis will be given identifying events in which polarity is an important feature and consequently, in which gravity may be a causative factor. These include compaction and polarization during cleavage, establishment of the radial axis, the embryonic-abembryonic axis, the dorso-ventral axis, and the anterior-posterior axis, implantation, and the later rotation of the embryo. The experimental data on these morphogenetic steps will be discussed and an assessment of the possible involvement of gravity will be made.

Frequency of bifurcated muscle fibers in hypertrophic rat soleus muscle

The total number of bifurcated and nonbifurcated fibers were counted in rat soleus muscles induced to hypertrophy by surgical ablation of the gastrocnemius and plantaris muscles. Sham-operated and normal soleus muscles served as controls. Every muscle fiber within the entire muscle was individually examined and counted with the aid of a dissecting microscope following a 10-12 hour nitric acid digestion of the connective tissue. The results show that the total number of muscle fibers in the hypertrophic soleus did not differ significantly from the control. The frequency of bifurcated fibers observed in the control muscles was significantly greater than has been previously reported, and their frequency in the hypertrophic muscles, although slightly increased, was not significantly different from control values. These data confirm that fiber hypertrophy is not accompanied by hyperplasia, and they further suggest that bifurcated fibers probably play an insignificant role during muscle adaptation to hypertrophy due to their very low frequency.

Cinemicrographic study of the cell movement in the primitive-streak-stage mouse embryo

Migration of the mesoderm cells in the primitive-streak-stage mouse embryo was directly studied by cinemicrography using whole embryo culture and Nomarski differential interference contrast optics. Relative transparency and small size of the early mouse embryos enabled direct observation of the individual cells and their cell processes. Seven-day-old mouse embryos were isolated and cultured in a small chamber in a medium consisting of 50% rat serum and 50% Dulbecco's modified minimum essential medium. The mesoderm cells move away from the primitive streak in both anterior and antimesometrial (distal) directions at a mean velocity of 46 micron h-1. They extend cell processes and constantly change cell shape. They do not translocate extensively as isolated single cells, but usually maintain attachment to other mesoderm cells. They show frequent cell division preceded by rounding up of the cell bodies, and accompanied by vigorous blebbing before and after cytokinesis. This study shows that it is possible to examine the motility of embryonic cells inside the mammalian embryo by direct observation if the embryo is small and transparent enough for the use of the Nomarski optics.

Sarcoidosis of the tongue--a case report

A case of sarcoidosis, unusual in that it was confined to the tongue, is reported in a 50 year-old female. The condition resolved after 1 year of steroid therapy and excision of fibrous tethering bands. Intra-oral sarcoidosis should be considered in the differential diagnosis of lingual swelling and induration.

A quantitative ultrastructural analysis of satellite cells in denervated fast and slow muscles of the mouse

Mononucleated cells located between the external lamina and sarcolemma of denervated muscle fibers within the extensor digitorum longus (EDL) and soleus muscles of adult mice were quantified and examined ultrastructurally from 3 to 65 days after ligating and removing a section of the sciatic nerve. During the first 2 weeks postdenervation, mononucleated cells in denervated muscles were morphologically indistinguishable from satellite cells observed in control muscles. With time, however, many of these satellite-like cells appeared more active as evidenced by a decrease in their nucleocytoplasmic ratio and an increase in their mean percentage of euchromatin material. The number of satellite cells (expressed as a ratio of satellite cell nuclei to satellite cell nuclei plus myonuclei) did not increase significantly until 30 days postdenervation, at which time the mean percentage for the soleus muscle had risen from a control value of 4.1-8.5%, and for the EDL from 1.2-4.1%. Small-diameter, presumably regenerating, myofibers were occasionally observed but only after 30 days denervation. The ultrastructural evidence plus comparisons of euchromatin distributions between myonuclei and satellite cell nuclei support the concept that an increase in the number of satellite-like cells during denervation is more likely due to satellite cell proliferation than to the formation of mononucleated fragments utilizing preexisting myonuclei.

An open study of the use of ceftazidime in Gram-negative infections

An open study of the use of ceftazidime in patients with Gram-negative infections was undertaken in a district general hospital. Ceftazidime was used in three groups of patients: 17 adults with infections due to Pseudomonas sp. or multi-resistant enterobacteria, three children with cystic fibrosis who had chest infections, and two premature neonates with severe pseudomonal pneumonia. The infections in the adult group included respiratory tract (6), urinary tract (4), wound infection (3), abdominal sepsis (2), osteomyelitis and panophthalmitis. In this group, ceftazidime was given as 1-2 g tid intravenously. In three patients, gentamicin was used concurrently and in four metronidazole was added. 76% of the adult group achieved complete clinical cure, all three cystic fibrosis cases improved markedly, and the two neonates showed complete resolution of the pneumonia. No adverse biochemical or haematological side effects occurred, although one patient developed an urticarial skin rash on the last day of a ten-day treatment course which resolved after discontinuing the ceftazidime.

Axial abnormalities following disturbed growth in mitomycin C-treated mouse embryos

Primitive-streak and early-organogenesis-stage mouse embryos were treated with Mitomycin C (MMC) by intraperitoneal injection of pregnant females. Skeletal preparations of newborn pups were made and the axial skeleton examined. The treated animals showed a high incidence of:- (1) changed vertebral numbers, (2) malformation of the vertebral column, (3) changed rib numbers and (4) rib abnormalities. These skeletal disturbances tend to be located more posteriorly with later MMC treatment. There is regional variation in the susceptibility of vertebrae to abnormal development. Extra elements may occur in any region of the spinal column and several unique combinations of numbers are reported. The possible origin of these abnormalities and their similarity to some human syndromes is discussed. It is suggested that they may be the consequence of altered growth profiles in interacting tissues during the restorative growth following MMC treatment.

Bacterial meningitis--ten years experience

Between January 1968 and December 1977, 635 cases of acute bacterial meningitis were admitted to hospitals in the Birmingham Area Health Authority. The epidemiology of these cases was analysed and compared with the 270 cases which were admitted to the regional infectious diseases unit at East Birmingham Hospital (E.B.H.). In children and young adults the meningococcus was the commonest causative organism while over the age of 25 pneumococcal meningitis predominated. Although Haemophilus influenzae was the second commonest infecting organism it was a rare cause of meningitis in school children and adults, only four cases presenting in these age groups in the Birmingham Area. A detailed analysis was made of the symptoms, signs, laboratory investigations and clinical course of the 270 cases treated at E.B.H. The mortality in the patients with pneumococcal meningitis was 30%. In the meningococcal group it was 3.5% and in the haemophilus groups 7.7%. An analysis of the various treatment regimes employed in the 270 E.B.H. patients supports the view that a single antibiotic is sufficient for the therapy of most forms of bacterial meningitis. Intrathecal antibiotic administration is unnecessary in pyogenic meningitis caused by meningococci, pneumococci or H. influenzae.

Satellite cell distribution within the soleus muscle of the adult mouse

The frequency of satellite cells was quantitated by electron microscopy in five proximal to distal regions of the soleus muscle of adult mice. In all, 236 satellite cell nuclei and 4, 475 myonuclei were counted on 51 transverse thin sections. The mean percentage of satellite cells, as a ratio of satellite cells to myonuclei, per region was found to be 5.4%, 5.3%, 5.0%, 5.2% and 4.9% for the most proximal to distal areas, respectively. Analysis of variance revealed no significant differences between either the regions or the animals studied. The number of satellite cell nuclei per cross-sectional area of muscle was also calculated for each of the five regions, and these values did not vary significantly from the proximal to distal ends of the muscle. Despite the fact that satellite cells were frequently noted in close association with cross-sectional profiles of myoneural junctions, this study establishes that the number of such perisynaptic satellite cells was not large enough to affect significantly the mean percentages of all satellite cells counted within the motor endplate regions(areas 3 and 4) of the soleus muscle. It is concluded from this study that satellite cells are uniformly distributed throughout the whole muscle.

Autonomous development of parts isolated from primitive-streak-stage mouse embryos. Is development clonal?

The relationship between growth rate and regionalization of amphibian, bird and mammalian embryos is briefly reviewed. In contrast to the others, mammals start gastrulation with few cells but accelerate cell proliferation coincidentally. Experiments are described which demonstrate (1) autonomous development of pieces isolated surgically from such mouse embryos, and (2) an absence of regeneration or regulation. Since such embryos regulate completely after chemically induced random cell death it is postulated that these results reflect developmental determination and a resulting mosaicism that suggests development may have a clonal basis. Maps are drawn, allocating positions to various tissues in the embryo.

Proliferation and migration of primordial germ cells during compensatory growth in mouse embryos

Primitive-streak-stage mouse embryos were treated with Mitomycin C injected intraperitoneally into pregnant females at 6.75--7.0 days post coitum. The newborn mice developed poorly and mortality was high during the suckling period. Many weaned survivors showed impaired fertility and poor breeding performance. Histological examination revealed a paucity of germ cells in the adult gonads. The deficiency was mainly caused by a severe reduction of the primordial germ cell population in early embryonic life, which was not fully compensated for during the compensatory growth phase of the Mitomycin C-treated embryo. Also contributing to such impaired fertility were retarded migration of the primordial germ cells into the genital ridges, poor development of the foetal gonad and secondary loss of the germ cells during gametogenesis in males.

The in vitro culture of primitive-streak-stage mouse embryos

The in vitro growth and morphogenesis of mouse embryos from early primitive-streak stage to early-somite stage is described. The embryo culture method employs a static culture system, a conventional chemically defined medium (Dulbecco's modified Eagle's medium), supplemented with additional glucose, glutamine and suitably prepared serum. The method of serum preparation is important for successful culture. Both mouse serum and rat serum support good development of primitive-streak-stage mouse embryos. Over 60% of early-streak stage and about 90% of late-streak stage grow and develop for 48 h in vitro. During the first 24 h in culture, total growth of the embryos as reflected by protein content, size and morphology is the same as in vivo.